The first one sounded familiar and I've definitely read the plot summary of this before, but not the book so I don't know if the rest of that description applies: https://en.wikipedia.org/wiki/The_Mote_in_God%27s_Eye

The other one appears to be https://www.goodreads.com/book/show/15744759-three-worlds-co... (summary and review at https://www.reddit.com/r/CharacterRant/comments/up854p/three... )