I'm not in NA but I'm also not in Japan and can confirm there is lag. The game is perfectly playable if you're not hoping for world first clears, so long as you can communicate in Japanese. If you can't, it isn't going to provide the same experience as an English-majority server at all.

When I moved servers (I originally started on Masamune - another JP server - but it was full when my friends joined) I made alts on a few to 'audition' them and compare the communities. There was a substantial difference in atmosphere immediately after zoning in, even in Ul'dah, so I picked my new home quite carefully.