You'll need the adapter. SNES is region locked, it's just there are only 2 regions, NTSC & PAL. For some reason Nintendo decided to only use a different shaped cart as the lock on NTSC system. Of course when it came to the PAL system, the same again was too easy and it has a different lockout chip.
Colour encoding and refresh is decided by SNES hardware, not game. A PAL game in an NTSC Snes will output NTSC60. There may be other problems, like mention above, some games check the refresh and will complain. If you get past that (I think that adapter can patch in memory), some pal games glitch when forced to 60. I think Mario all-stars has graphical glitches forced to 60.