1 - The only thing inevitible is change. Primitive Plus is officially suported WildCard should expect updates to roll down hill to Unrestricted.

2 - There is no official list of what Primitive Plus Unrestricted works with since any mod you add to it effectively stops P+U from working by disabling all the P+U engrams and ignoring the Overrides.

3 - Official is NOT stackable and won't load at all with other Mods. P+U is stackable, loads with other mods.

* * Your Post Title is misleading and causes one to think you got P+U working with other mods.

Basically what Briana said. If you wants mods then the unrestricted version is what you use. If he made this one stackable as well then effectively they would be the same. If you want to keep it simi primitive and add mods then use the unrestricted and hide engrams that you don't want.