We are on the same page. I try to limit intelligent humanoids in my settings too. For me, it is about resources and scarcity. I want it to make internal sense to me.
I have a somewhat larger number of species for my games but only because my settings have very close ties to Faerie (FeyWild for the new kids). In that sense, they may live on both planes. I also have the Aethyrial plane that is close to the Prime. I pulled that concept from the excellent Deverry novels by Katharine Kerr.
I still have limits and I do not run kitchen sink games.
Sometimes I do incorporate Planescape into my cosmology as well. It just depends on the theme I am running as sometimes the settings have been completely cut off from the planes.
I really do get the need for limitations to make internal sense. Unlike you, my settings are mainly background consistency and are not completely formed and a living setting.
I've tossed around ideas for a completely different campaign now and then, kind of a mashup of Spelljammer and a few other ideas to make it my own. Maybe someday.


