[DRIFT_HUNTER]

Like the function name say SetPlayerTeam means to set player team (or change it)
If you use AddPlayerClass than when player select class his team id is set to NO_TEAM
But if you use AddPlayerClassEx than you have defined team id for that class (skin)

Here are some useful documentation for these functions
https://sampwiki.blast.hk/wiki/SetPlayerTeam
https://sampwiki.blast.hk/wiki/AddPlayerClass
https://sampwiki.blast.hk/wiki/AddPlayerClassEx

By the way players on same team can not kill each other ( No team kill )