For now I have just tried it in very low PC (1Ghz AMD APU: A6 1450).
I have configured a 486DX2 and a 386DX33 machine, 16 Mo and Tseng ET4000AX for both.
pcem switch well from interlaced mode (when in dos) and progressive 240p
I tested Desert Strike and Super Frog.
The emulation of the 486 is too slow.
With the 386, is still slow for desert strike.
super frog seems to play at nearly normal speed but the scrolling is bad.
When it will be possible, I will test on my new dedicated CRT PC (Pentium 3Ghz, Radeon R5)