Depends on the model of SNES, I BELIEVE the later 1 chip ones that do RGB natively can do Csync but need to have it restored with a mod.
To answer RoninChaos's other questions. You can get an overlay for the controller that will have english on it. You can find these on ebay or from
http://www.retrogamingcables.co.uk There's also english versions of the firmware so when you get yours and update its firmware make sure to do so with the english one.
If you order your framemeister from Solaris Japan you can buy one with the Dterminal to component adapter for a little less than buying them separately.
For your systems I would buy a csync RGB cable for your SNES, and use component for everything else you have listed.
The framemeister has a variety of inputs on it. Let's see if I can do this from memory but on the back are Dterminal (including audio jacks for it) and 2 HDMI inputs. On the front is the 8pin din for RGB, S-Video, and Composite. I'll note that the S-video and composite in share audio jacks.
Oh also note that the RGB to 8pin din that comes with the Framemeister is a JP21 adapter. It looks exactly the same as SCART but the pin outs are different. You can go with JP21 RGB cables, but they tend to be less common than SCART. So you just need to make a decision before buying your cables if you're going to go SCART or JP21. If you go SCART than you need to buy the adapter that NormalFish linked above.