Here's a thread over at another forum with good photos of this thingy:
http://benheck.com/phpBB/viewtopic.php?t=15332
Here follows my THOUGHTS on this system. I don't own one and have never seen anything else than the photos in the pasted link. I will not take responsibility for the accuracy of this information.
I sincerely doubt that the SNES slot has the tabs. It sounds un-clonish to ADD some kind of import protection like that when it's not needed. (No tabs=same case for all regions=lower production cost)
As I suspected, the system consists of two separate motherboards. The NES-ON-A-CHIP emits composite and composite only (as usual) straight from the chipset and there is nothing you can do to change that.
The SNES part however is using a CXA1145 which should be fairly easy to tap RGB from. S-Video is possible, but needs the addition of the same circuitry as a SNES-2. Gamesx have had an unfinished diagram for ages. If that diagram is ever completed or you complete it yourself, S-Video output is yours but only for SNES games.
According to the photos in the pasted link, it looks like as if FC Twin's SNES part is using the same layout as a generation 1 SNES (=PPU1, PPU2 and CPU instead of all baked into one big chip) which *should* make it possible to hook this baby up in the same manner as that with a 50/60Hz switch for all our European and Australian friends out there.
Verdict: Yes, this system should be able to run both US and Japanese games. PAL games will work as long as they are not import protected (this game pak is not designed for your super famicom or super nes) but if you can hook a switch to it, that problem is gone too.
S-Video and RGB mods are most likely possible, but for SNES games only. For the NES part, you're stuck with composite no matter what. Very cool and impressive piece of hardware indeed.