While I'm *pretty* sure PAL games won't run correctly on my NTSC system, will Japanese games (translated games) be able to run fine? Or perhaps both PAL and Japanese games can? Maybe there's a patch to make either Japanese or PAL games work? I'm not sure whether Japanese games are NTSC or PAL... I can't find any information on this looking it up on the internet, so thanks a lot! (might come across as a total newb here heheh)
All japanese games that have a supported mapper should work. Some european games might work some might not. It really depends on wether the game was pal optimized.
Japanese games are NTSC. Like Jeroen said, what could prevent you from playing them is that there are Japan-only mappers that might not have been implemented on the PowerPak yet. You can try all the games you want, it will not break your NES or your PowerPak (AFAIK), some will work, some will not, there is no characteristic that excludes a whole territory.