Whose love was the most for Shri Krishna, Radha or Meera?

 A layman thinks that Radha Krishna were lovers like any male - female only with the difference of having more intensity than others.” - This a common man thinks.

Though the reality of their connection is far superior than our imagination. If it's not so then nothing is unique with their relationship and its glorification is overrated…..

Isliye log aise sawal krte hain jaise yeh hai. (That's why people ask such questions similar this one)

Obviously, There is no comparison with Radha Rani. What she is for Krishna cannot be described in words.

All women in relationship with Krishna are at one side and on the other is Radha. Also it's to be noted that there are many kinds of love and attachment. The way Meerabai devoted herself into Krishna's feet is differ from Radha’s dedication. Meerabai’s unparalleled devotion has its own significance which cannot be compared with anyone. Whereas Radha is Radha. She is the life source of Krishna himself. So what else is there to say.

When (what age) did Rukmini fall in love with Shri Krishna? How long did she have to wait for him?

 According to Harivamsa Purana, Mata Rukmini was 16 when she married Bhagwan Sri Krishna.

“She who was difficult to be seen even by devas, was seen by Krishna with his mind. She was of sixteen years old. She was of white complexion. Her eyes were long and beautiful.”

Source : BORI CE Mahabharata Vishnu Parva

This is what Padma Puran says :

The beautiful-faced (Rukmiṇī) did not want Śiśupala as her husband. She, of a firm vow, was attached to Viṣṇu from her childhood. That virgin Rukmiṇī, dedicated to Viṣṇu, always worshipped the deities and gave various presents (to brāhmaṇas). Highly devoted to practising vows, and thinking of Viṣṇu, the lord of the soul, as her husband, she lived in her father’s house. Through his intelligent son Rukmin, the best king tried to get her married to Śiśupāla.

Ref: Pādma Purana Section 6 Ch 247 ( Debashis

Both Bhagwan Sri Krishna and Mata Rukmini loved each other.

Bhagwan Sri Krishna knew that Mata Rukmini is possessed of unrivalled beauty and uncountable virtues and hence he knew that she would be an ideal wife.

Lord Kṛṣṇa knew that Rukmiṇī possessed intelligence, auspicious bodily markings, magnanimity, beauty, proper behavior and all other good qualities. Concluding that she would be an ideal wife for Him, He made up His mind to marry her.

Source : Srimad Bhagwatam Canto 10 ch 52

Mata Rukmini in her letter herself admitted her love for Bhagwan Sri Krishna. She had fallen in love with Bhagwan Sri Krishna as soon as she heard about his divine qualities, unrivalled beauty and infinite virtues.

Śrī Rukmiṇī said [in her letter, as read by the brāhmaṇa]: O beauty of the worlds, having heard of Your qualities, which enter the ears of those who hear and remove their bodily distress, and having also heard of Your beauty, which fulfills all the visual desires of those who see, I have fixed my shameless mind upon You, O Kṛṣṇa.

O Mukunda, You are equal only to Yourself in lineage, character, beauty, knowledge, youthfulness, wealth and influence. O lion among men, You delight the minds of all mankind. What aristocratic, sober-minded and marriageable girl of a good family would not choose You as her husband when the proper time has come?

Therefore, my dear Lord, I have chosen You as my husband, and I surrender myself to You. Please come swiftly, O almighty one, and make me Your wife. My dear lotus-eyed Lord, let Śiśupāla never touch the hero’s portion like a jackal stealing the property of a lion.

Source : Srimad Bhagwatam Canto 10 Ch 52

So as soon as Bhagwan Sri Krishna and Mata Rukmini had heard about one another , they had fallen for each other.

The question asks how long have they waited for one another ? The answer should be since their birth.

Bhagwan Sri Krishna is Bhagwan Vishnu while Mata Rukmini is Ma Lakshmi herself. Hence they were destined to marry one another. They are inseperable from one another. The love between them is immesurable, divine, transcesdental, unique, amazing, unique, perfect , exquisite and beyond all descriptions.

Goddess Lakshmi is forever united with the Lord Vishnu. So, when our Lord becomes Rama, Sri becomes Sita, when He is Krishna, she is Rukmini.

Source : Vishnu Puran Book 1 Ch 9.

She, the Mother of the Universe, is the eternal companion of Vishnu. Just as He is omnipresent, so is She.He is meaning, She is speech; He is behavior, She is morality; He is understanding, She is intellect; He is dharma, She is good deeds.

Source : Vishnu Puran Book 1 Ch 8.