So off hand I know 4 “features” that come to mind that are missing on 1000nxi:
- custom full screen engine pages as you mentioned, these seem to come with SU14 or more specifically the new SR22, so hopefully will enable other devs to create these too for their aircraft
- glide features (Safe/Smart Glide). While it was initially reported that these would come too, they have since said this was a mistake and will not arrive
- many times on youtube you can see pilots use some sort of split/mini map display where FPL and map are displayed concurrently
- Checklists
Oh, and the 750 has nothing to do with this aircraft, but since you brought it up the TDI 750 is basically the real garmin trainer unit running in the background, so it is as close to their real deal as you can get. But it has other major downsides, but this is the wrong thread for this so suggest you inquire elsewhere about that particular unit.