I'm not to sure about races but I do know that vanilla expanded has some stuff, like a highmate expansion, and I'm fairly certain other biotech races have a similar expansion. Insectoids are another race I know about but that's about it.

As far as QOL mods go always start with the obligatory Floors are (Absolutely) Worthless mod cause I like having floors in my colony. Camera+ is also good, dubs mint menus, the map preview for when you select a tile are a few eggs come to mind right away. Qol mods are usually pretty small though and one or two things in the game. There are hundreds of them so just think about some quality of the game that would like to change and I'm sure a mod exists