Hi, well, this is my opinion
If you use emulators like Kega, Mednafen, etc i dont think using exact refresh rate will make any difference
A 15khz CRT TV have a "resolution" of 240 lines in NTSC and 288 in PAL
In my setup, i have 2536x240@60hz and 2536x288@50hz, and adjust emulators to this resolutions. You can add 2536x480/2536x576 for high res
About saturn, deppend emulator, SSF sadly dont support low resolutions, only interlaced