>>91378476nerd rant:
Tact Shooters are the games that rely on things like: positioning, economy, and obviously "tactics". They are mostly round based and most of them are 1 life per round. Prime example is Counter Strike
Hero Shooters are basically dependent on team comps, objective fighting and obviously the usage of abilities per character. The prime example is Overwatch as you said
They somewhat mix each with one and other to create a "new thing" but it is basically like how Romance and Comedy are commonly associated in the entertaining business creating the romcoms, but can exist on their own. They just work well together because it just works, Valorant and R6S are examples of it.
Rivals is pretty much like Overwatch in being just a Hero Shooter.