@ILTG The team switching and gamemode changing are done by command blocks, either hooked to a clock or set to "repeat" and "always active." (Or whatever the two are.)

The command(s) for gamemode basically change anyone within a certain radius who is in survival to adventure mode, and vice versa. (/gamemode @a[r=15,m=s] adventure -- Changes all survival players within 15 blocks to adventure)

Pretty inefficient for managing game modes, the system I have can put a custom sized protection or spawn zone anywhere in any dimension, it can also put an anti spawn zone inside a spawn zone. (PVP Arena) It can even work based on player tags and player scores. (you could have a team that could be immune from getting their gamemode switched) It also can have a cool down so it instantly changes your gamemode to adventure but give a grace period when changing back to survival.