Dual wielding pistols sounds pretty fun to me so I think I would go down Nisha's middle skill tree first. If I was going to play with others I would most likely go with Claptraps right tree since it seems like a good support character archetype.
I thought it would be a lot more noticeable when someone had better gear but it just felt like normal PvP. The supreme victory of Lincoln Force.ru was also a nice bonus. It doesn't happen often but having a full team is really fun.
I've liked every Ys game that came out over here so I expect this one will be pretty good. It kinda looks like it'll just be upgraded port of the vita version going by the way it looks but that's fine. After all Ys is all about the boss fights.
It does seem like you'll have a better time in PVP once you get to a higher level although that shouldn't matter. Once I started using the fusion rifle up close and the scout rife at range I started to at least remain in the middle of the pack during pvp. I even managed to get the top spot one time which is kinda amazing since I never play very much competitive mutiplayer. Also make sure you keep tabs on the radar since if you know someone is coming it's easier to react to them.