The concept of vaishnavising Lord Shiva is a much later stance broughtup by the likes of Madhva, Vallabha, Tulasidasa and fanatic poets like Kanakadasa, Purandaradasa etc:
Earlier when sectarian cult of Vaishnavism began dating to 10th CE, prime Vaishnavas like Yamunacharya (Guru of Ramanuja) and the likes demeaned Lord Shiva as much as possible unable to tolerate the countering hatred they had to spread unable to bare the pain caused by toxic Shaivite kings like Krimikantha Chola etc:
“Rudra is a deluding deity and he's very well versed in doing such things with his followers”
—— Yamunacharya (Agama pramanya 83).
So it is safe to conclude that these Vaishnavas were mumbo jumbo or wishy washy emotional fanatics who didn't even hesitate to spread hatred about Lord himself just because some of the bigoted kings like Cholas tortured them. I wonder how they get revered as gurus or siddhantins.
Coming to your question, not just Padma purana 5.114 or Shaiva Puranas but all other so called Sattvika (Vaishnava) puranas which are bracketed by Pancharatrikas ultimately end up stating Lord Shiva alone as supreme.
But why? Because it's the supreme declaration from Vedas (Shrutis themselves). Atharvaveda 15.6.4 says:
स बृहतीं दिशमनु व्यचलत्। तमितिहासश्च पुराणं च गाथाश्च नाराशंसीश्चानुव्यचलन् । इतिहासस्य च वै स पुराणस्य च गाथानां च नाराशंसीनां च प्रियं धाम भवति य एवं वेद ॥४॥
4. He (Shiva) went away to the great region. Itihāsa and Purāna and Gāthās and Nārāsansis followed him. He who, etc.
Now let us look at each and every Vaishnava Purana which are proclaimed to be saatvika by its followers.
Oh all pervading Lord! When you, through your own Potency consisting of three guṇas, undertake to create, preserve and destroy the universe, Oh self-seeing perfect Lord, you assume (severally) the appellations Brahmā, Viṣṇu and Śiva.
You are that Supreme mysterious Brahman, the creator of beings, of the higher (gods) and the lower order (sub-human beings). You are the supreme soul who appear as the universe by means of your various powers (such as Sattva, Rajas and Tamas). Hence you are the Controller and Master of the Universe.
~ Srimad Bhagavatam 8.7.23-24
Shiva has no Equal or Superior
- Your brother-in-law god Rudra whose shining mass of hair (on head) became scattered and tawny by the dust raised by the whirl-wind in śmaśāna (the crematory ground) and whose pure gold-like body is smeared with ashes, witnesses (everything) with his three eyes (viz. the Sun, the Moon and the fire.) Hence there is no secrecy anywhere.
- In this world there is no one who is his relative or non-relative. Nobody is specially respectable or censurable to him. By performance of various vows, we desire to have the (prosperity and greatness of) Māyā which he has enjoyed and spurned (lit. kicked). 26. Thoughtful people who wish to tear off the veil of Māyā praise his life which is spotless or unattached (to sensual pleasures). He has none equal or superior to him. He is the ultimate goal of the saintly people; yet he himself followed the vow of piśāca type of life.
~ Srimad Bhagavatam 3.14.26
Shiva is the Lord of the dieties
[Rāma says] 165. I seek the refuge of that Śaṅkara, who affords protection, and having saluted the feet of whom, the granter of boons, with devotion, and having praised whom with chaste words, the careful, blazing sun, removes the darkness with his rays. 166. (O god) those stupid men of impure minds, who, due to their close attachment to grandeur, pride and trade, do not recognise you to be the lord of the best gods and of this mobile and immobile world, (later) experience tortures of hell.
~ Padma Purana - Sṛṣṭi-khaṇḍa - Chapter 33
Shiva is his own Lord other than whom no one exists
I salute the eternal Śambhu, the extreme limit of Brahman, the revered one, the lord, the lord of Hiraṇyagarbha, the three-eyed one, and also seek the refuge of (you), wherefrom the world has originated, and unto whom it will perish (i.e. merge), and by whom, i.e. Śiva, this entire (world) is pervaded. I salute you, who are without any characteristic mark, whose form cannot be seen, who are your own lord and of that of the soul, who are of a uniform nature, who are beyond Brahman, and who are the highest lord, other than whom nothing exists; whom the meditating saints who have become one with the highest soul, giving up meditation along with mystical letter forming the essential part of the hymn, after securing concentration see.
The Devotee who sung This Praise of Shiva merged into him and was instantly liberated.
45-47. Thus having praised the revered Kapardin, Śaṅkukarṇa also prostrated himself on the ground and uttered the highest (syllable) Om. At that moment only the great Linga of Śiva appeared there. It was knowledge, joy, and very much like the fire having a crore of flames. Śaṅkukarṇa’s soul was liberated. His pure soul moved everywhere. It merged into that pure Linga. (Thus) a great wonder took place.
~ Padma Purana - Svarga-khaṇḍa - Chapter 35
Shiva is PURUSHOTTAMA
त्वमादिदेवः पुरुषोत्तमो हरिर्भवो महेशस्त्रिपुरान्तको विभुः । भगाक्षिहा दैत्यरिपुः पुरातनो वृषध्वजः पाहि सुरोत्तमोत्तम ।। २५.१९ ।। गिरीशजानाथ गिरिप्रियाप्रिय प्रभो समस्तामरलोकपूजित ।
Devas say to Lord Shiva: You are the first among of Gods, Purushottama, Hari, Bhava, Mahesha, Destroyer of Tripuras, the enemy of the demons, the most ancient, the bull-bannered. O great God, protect us.
~ Varaha Purana Chapter 25.
Shiva is the Bestower of Chatur-vargas (Dharma, Artha, Kama, Moksha)
स्थूलसूक्ष्मविभागाभ्यामनिर्देश्याय शंभवे ।।भवाय भवसंभूतदुःखहन्त्रे नमोनमः ।। २२१ ।। तर्कमार्गातिदूराय तपसां फलदायिने ।।चतुर्वर्गवदान्याय सर्वज्ञाय नमोनमः ।। २२२ ।। आदिमध्यांतशून्याय निरस्ताशेषभीतये ।।योगिध्येयाय महते निर्गुणाय नमोनमः ।। २२३ ।।
Obeisance, obeisance to Bhava, to Sambhu who cannot be specifically distinguished in gross or subtle form and to one who is the remover of all miseries of worldly existence. Obeisance, obeisance to one who is far away from the way of dialectics, who is the bestower of the fruit of austerities, who is the liberal bestower of the fourfold aims of life and who is omniscient.
~ Narada Puraana III.91.223
Sadasiva is the Origin of Brahma, Vishnu and Samhara Rudra
He who is that eternal god Sadāśiva, who is saluted by Brahmā, who has three eyes, who is the prop of virtues, who is beyond qualities, who is unchangeable and immutable, had once a desire to create on seeing the three qualities in himself—this triad of qualities should be known as the three Vedas. O dear one, having divided himself and the region there, he created on his right side the son, viz. Brahmā and Hari from his left side. At the back side he created Maheśāna (i.e. Śiva); thus the mighty one created three sons. As soon as they were born they became the three gods—Brahmā, Viṣṇu and Śiva. They distinctly spoke these words: “Who are you? Who are we?” To those sons Śiva said: “You are the sons, (and) I am your father.
~ Padma Purana - Pātāla-Khaṇḍa
Obeisance, obeisance to the one who is devoted to his devotees, to one who is the bestower of worldly enjoyment and liberation, to the lord of all worlds, to one who is without garments and to one who is the final resort. Obeisance, obeisance to the origin of Trimurtis (the three deities of Brahma, Visnu and Rudra) to one with three eyes, to the light of three lights (sun, moon and fire), to the remover of the cycle of births.
~ Narada Purana III.91.227-228
All Gods Including Brahma, Vishnu, Lakshmi, Sarasvati Serve Shiva
A crore of beings would remember the lord of Umā who is like this. Having obtained desired pleasures they are honoured in Śiva’s heaven (Shiva loka). Brahmā, Viṣṇu, great Indra are the door-keepers of his city. The two goddesses Lakṣmī and Sarasvatī are appointed to worship the threshold etc. on the ground. Gods and celestial women are the servants of the god of gods. All gods are the servants of the noble one.
~ Padma Purana - Pātāla-Khaṇḍa - Chapter 109.
Worship of Shiva Leads To Bhukti and Mukti
शिवार्चनं प्रवक्ष्यामि भक्तिमुक्तिकरं परम् ।। शान्तं सर्वगतं शून्यं मात्राद्वादशके स्थितम् ।। 22.1 ।।
I will now describe the great adoration of Shiva which yields enjoyment and emancipation. He is of a quiescent soul, present every where, void and stationed in a room of twelve parts.
~ Garuda Purana Aachar Khanda, Chapter 22.
Shiva Is Everything
For A Devotee of Shiva, Shiva is indeed Everything. Hence the Following Contemplation is prescribed For A Devotee of Shiva by Garuda Purana.
शिवो दाता शिवो भोक्ता शिवः सर्वमिदं जगत् ।। शिवो जयति सर्वत्र यः शिवः सोऽहमेव च ।। 23.28 ।। यत्कृतं यत्करिष्यामि तत्सर्वं सुकृतं तव(तस्तवम्) ।। त्वं त्राता विश्वनेता च नान्योनाथोऽस्तिमेशिव ।। 23.29 ।।
Shiva is the giver, Shiva is enjoyer and Shiva is the entire universe. Shiva is victorious everywhere. I am myself Shiva. O Shiva! thou art the saviour and the leader of the universe. Apart from you, I have no other lord.
~ Garuda Purana, Aachar Khanda, Chapter 23.
Namah Shivaya!.