v2 is the one most people are playing now considering it's the most updated out of the two (as obvious as that may sound), so i'd say go for that version. i'm unsure if people do in fact play v1 online, but as far as i'm aware v2 is the one mostly used.
in regards to playing 'spot the region'...
NTSC-J games will have a mark similar to this on either side.
NTSC-U games will have this alongside the bottom.
for the sake of being throrough;
PAL games will typically have this on the bottom.
it's not always consistent (sometimes the NTSC-U discs just say 'dreamcast'), but regardless i hope this helps a little bit in your search, and doubly so for your experiences playing PSO.