I’ve just been playing with the options and it would appear that both PMDG and Fenix do use lower resolution internal models for their static and AI aircraft.
However, both do appear to still draw the flight crew and the cabin on the Fenix did appear to be of a fairly high quality, despite the fact that i had chosen to hide the cabin on my aircraft.
Could applying that hidden-cabin setting to the other multiplayer, AI and static aircraft save more performance? If i’ve decided i can do without seeing my own cabin, it’s a pretty safe bet that I won’t be too bothered about looking at anyone else’s. 