-Tried Retroarch Citra core on PS4 PRO Linux (GL drivers).
New Super Mario 2 runs at almost 30-40 FPS. (50-60% speed). Something is unoptimized....
-However, Flycast ran well the few Dreamcast games I have (tried Heavy Metal Geomatrix and Zombie's Revenge). Flycast usually has some bugs with some games like Spawn in the Demon's hand, and some games run slow like Crazy Taxi.
-Saturn converted packages, also ran well : Tried Nights into Dreams, Guardian Heroes, Clockwork Knight. They all ran at full speed.
Hopefully Citra core gets ported someday to PS4. Setting up Linux on PS4 is time consuming, and you're not sure to get the most optimized results.