Vanilla with patch 1.2 is perfectly fine to play.
Revival, or Unofficial Revival, or Lost London, or Nagahaku's mod, but only one at a time. They do have different gameplay experiences.
Regarding 2038, it works fine, but your connection will have some impact. Some people have complained about their ping, but this isn't a twitch shooter, I think it's fine.
Global, well you have to pay for it, and it's not worth the money in my opinion.