Lore behind the Nine Hells and the Abyss in 5e

Hi all,

So I'm going to try and run a home-brew campaign that borrows elements from a few holy books. Think angels versus demons for simplicity's sake.

My current understanding is there are 9 hells and the lower you go the worse it gets, with Azmodeus essentially being the king of hell by ruling over the lowest tier. The hells all contain different devils and do not contain demons.

Whereas the abyss is endless, has various rulers that rise and fall to power based on their ability to conquer other demons, the abyss does not contain devils.

What I was hoping you guys might be able to help me out with is how exactly these two planes interact if at all, (and what relationship devils and demons have) and in particular any lore behind how they came to be i.e. I know that angels and/or some form of heavenly power created Azmodeus but I don't know much more than that.

Essentially I'd love a cosmology 101 in 5e from you guys on all things devilish and demonic (I've read the stuff on the different planes on the PHB). I appreciate that's a huge question so if you have any links to wider reading I can do instead I'd greatly appreciate it!

Thanks!