Awesome find!
I use an NES power brick with my SFC and it works fine so I'd reccomend just using the one you have. The US SNES power supply wont work because the plug to the console is larger than the JP plug.
Check out this site for some good game ideas.
http://www.asahi-net.or.jp/~uw7g-bwr/sfc/games.htm
Macross: Scrambled Valkyrie, anything Parodius, Gundam Wing: Endless Duel, Assault Suits Valken, a.k.a. Cybernator and of course with an import adapter you can play any of the US SNES games.