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.