Basically to clear your confusion about same looking agents..... There are 2 different earths or like another dimension alpha and beta earth. Therefore each agent has a copy of itself in the other earth which are like the villains. They steal radianite from the other earth by planting that bomb and the defenders defend or defuse it.
When the poison girl (who is called Viper) said that she'll "handle the parasite", she was specifically referring to Reyna (the purple aesthetic girl). She was telling the others to divide and conquer, and just happened to call Reyna an insulting name.
i think u were confused cuz the cinematics dont contain as much lore as like the game does in the game u can like read about stuff u can read about the characters and etc every character has its own like purpose in the game lol. the game itself is like cs:go but the lore itself is pretty interesting
8:58 that green girl is the other version just like how the african guy saw his own self... basically in valorant there are like 2 worlds and the other one is trying to take radianite away from the first one and like are basically terrorists trying to blow up stuff there are like 2 versions of each character from what i know 1 is good 1 is bad