Thanks for forcing me to not give up! I downloaded a few titles and some of them really work.
Crazy Cars I, II, III - unfortunately, out of scan range and bye bye for all three of them
Chase HQ II - some corrupted graphics in the beginning but then works amazingly smoothly, 60 FPS
Duck Tales - yes, that worked too
F1 GP - intro doesn't work but the game itself does. Surprisingly, even on 50 MHz it's not shockingly fast, max 18 FPS I would say
Hard Drivin II - super smooth, 60 FPS
Lotus II - super smooth, 60 FPS
Race Drivin - nope
Test Drive - quite all right although not super smooth
Test Drive II - terribly slow, something is really wrong with this game
Turbo Outrun - nope
(and as mentioned, Lotus III - nope)
The best feeling I had from Lotus II, great playability, speed, smoothness and very few rounding errors (what is quite common in other games - everything is super smooth so you can see how the rounding jumps when zooming sprites).
What an irony. Centek installed the turbo TOS 4.x as an emergency option (no fast ram, who would use that, right?) and now it serves me perfectly for trying out old games (which of course hate TT RAM of any sorts).