how to play stellaris lithoids on os x high sierra

You do get more bonuses if you form and level up a Federation, get galactic laws passed etc, but it's perfectly viable to basically keep out of galactic affairs until you're ready to steamroll, at which point you pick the Colossus ascension perk. not genocidal, not Driven Assimilator, not Fanatic Pacifist, not Inward Perfection) doesn't force you to be especially diplomatic. It should also be said that playing as an empire with normal diplomacy (i.e. Note: Inward Perfection empires can raid pops as well using Nihilistic Acquisition, so you can still be somewhat aggressive even as nominally 'pacifist' it's just you generally can't conquer planets, so your mid-game plan will probably rely heavily on megastructures. If you prefer a slower game but still without much diplomacy, Barbaric Despoilers and Inward Perfection are decent options. Also, if you're going to play genocidal as you said in the OP, it's already kind of implied that you're going for the 'kill everyone ASAP' plan Terravores are just the more extreme version of this.

It's just that they don't really have a distinct playstyle from how it would be with a bio main species, just a few quirks here and there. Don't get me wrong, Lithoids work just fine as the main species of a normal empire.

How to play stellaris lithoids on os x high sierra