How many versions of the game are there?
There are two primary versions of Super Dragon Ball Z -- the arcade version, and the PS2 version. While there are three PS2 releases (NTSC-J, NTSC-U and PAL), there aren't really any notable balance differences between them. The PAL version is generally not recommended, though, as there are some unintended bugs and poor behaviour stemming from the jump to 50Hz.
Are there any differences between the arcade and PS2 versions?
Aside from the six console-exclusive characters (U.Gohan, Videl, Buu, C.Frieza, K.Piccolo and M.Vegeta), there are no major balance changes between the arcade and PS2 versions of the game.
How do you play online?
Online play is conducted through a special netplay build of PCSX2 and ZeroTier VPN. Be sure to join the Discord server to ask questions, get help if you need it, and most importantly, organise games!
Is there a tier list for this game?
Below is a tier list devised by top Japanese player Kabe back in 2020. Bear in mind that this is for the arcade version of the game, so console-exclusive characters are currently unranked.
S: Cell
A: Goku, Trunks
B+: Android 17, Android 18
B: Piccolo, Android 16, Vegeta, Frieza
C: Krillin, Chi-Chi
G: Gohan
Generally speaking, most characters are seen at high levels of play, as a strong understanding of the game systems and your character's options is more valuable than the overall strength of each character themselves. Top players such as Kabe, Nyakki and Whitefreeza frequently do quite well with lower-tier characters (Kabe in particular is infamous for tricking people into thinking Chi-Chi is top tier). The only outlier is Gohan, who is seen to be notably weak compared to every other character. While he does occasionally see play, it's mostly for jokes.