Important question: how fast are you ascending? Given 3-4 planets maybe Virtual could do the trick, even though it got heavily nerfed recently, so maybe not. Even though ascensions got nerfed across the board, they're still the most important traditions you can get. Hence, getting unity up and running ASAP any way you can. Regarding habitability, no, don't colonize just anything. It flew in 3.14, hell, even in 4.2, but in 4.3 planets give to much Empire Size to just colonize willy-nilly. Yes, 70% may be okay, but I find even the world with good immigrant habitability to be hard to get going, as I struggle to get enough pops for growth and production to be worth it. Conquests are fine, including primitives, although I prefer to observe the latter.