Regarding physical features, I only heard that sims perceive the weight slider. Sims with the slider in the center get some bonus, those at the skinny or voluminous ends get a malus. Can't be much though. I never heard that other sliders play a role, but who knows. There are some obvious candidates, like how muscular a sim is. Sims also have a fitness stat. I can't imagine hair plays any role.
I should probably check whether there's some trait incompatibility between my founder and Tay, because I know for sure that every single autonomous conversation they had went south, even when Tay was a teen.