Thats a good question. I don't know because I never had a rtg card. I run in 64 colors on my a1200 in aga screenmodes.
I just checked, and on winuae on my amigasys install, it works fine, switching and loading the demos properly on whatever screen they start on. Then it goes back to your picasso desktop.
Also perhaps of relevance, on my linux install I am just using the amiga os 3.x install from amiga forever, since amikit/amigasys are a bit tricky to install on linux.
Steven