ive spoken before about my belief about hells, here's my belief on the heaven realms:
-there are some low heavens which are purely places of enjoyment without much sinning where good karma is exhausted. people are born with good inclinations, but not much more knowledge than on earth planes. they largely neglect yoga because they are distracted by sense indulgence and because they have no desire to stop suffering because they suffer little. when hindu texts say that its preferable to be born on earth than in heaven, they are referring to such.
-in higher heavens then these its common for at least some memories from past lives to be kept, starting with heavens like pitr-lokas where virtuous people are reuinited with past virtuous loved ones and virtuous relatives. they benefit from prayers for ancestors but are NOT dependent on them.
-there are some high heavens which are places of wisdom and virtue, pure lands home to sages and embodied buddhas. many celestial beings reside in such places and supernatural powers are very common.
-the very highest heavens are transcendent places where the greatest devas reside, where no one has a form (arupa heavens) and where the holy luminous presence of God is apparent to all. absolutely none return to lower planes, all are liberated and thus merge into Brahman by merely being born there and spending time there. the greatest saints are reborn here. and this is the nature of vaikuntha/the kingdom of heaven.

to tangent a bit, I now think there is no brahma who is the creator in a trinity and the engineer of the universe anyway, God does the initial creation (creating the substance from Himself) as well as the secondary creation (engineering its evolution), though She lets other beings be tertiary creators in smaller ways, like devas, siddhas, and progenitors. God is also the primary and final destroyer and the primary sustainer, and its a religious relic that the creator god is regarded as not the same as the Supreme Lord but Shiva and Vishnu are both regarded as equivalent to the Supreme even in inter shaiva-vaishnava discourse. of course the puranic literature differentiates between a Parashiva or Mahavishnu, of which there is only One, and a lesser form of Shiva/Rudra or Vishnu, the latter of which there is one for each universe, and they are involved directly in destruction or sustenance respectively which is governed by the former Para/Maha form, but the best thing to do is to do away with the trinity entirely. the Lord is one without a second!