once you make a character as it is now you can not delete it and you have an initial 4 slots for 4 characters, but you can buy extra character slots using battlefunds costing real $. so once you make a character and choose a faction your stuck with it. they are somewhat allowing players to email support and have characters removed but from what i can tell its more for the beta players who were left stuck with full players slots and it takes a while for them to do it.

and no once you are in the server there is no option to switch teams because you play as one of the 2 factions royals or nationals, each side consists of the same faction. your character is preset as Royal or national and saved that way, also each faction has different items to purchase in the store to enhance your appearance, you however can not purchase weapons to gain an advantage. each side has access to purchase the same weapon upgrades its the clothing that is different

by overall popularity the nationals are the favorite and seem to win rounds more often than not. the classes are Gunner, commando, and soldier.

Soldier is your medic having the ability to heal
Gunner is your anti armor
and commando is your overpowered stealth capable one shot knife killer.

The classes have recently been rebalanced with a patch just prior to release that crashed the entire game, and has subsequently unbalanced the classes pretty bad. the gunner and commando are now overpowered but there will be allot more rebalancing soon.