The rounds are timed and it is able to play pong while you are playing else you will spectate untill a new round starts. Once you advance in rank you can pick characters from a bigger choice. Characters ARE different because different ones start off with different weapons. Not as different as a scout from Hw but different. The selected character also determines what weapons are available for selection.
Different characters have different skills and abilities.
A character may be fast, but with bad aim. Also, different characters have a different choice of weapons. Hm think we have 4 characters in each team. We are not sure yet. At this point, after jumping off a high building you will lose a deal of speed for a moment.