Well if it's vs. NPC monsters, you can use a rule set like D&D. All the basic rules are here:
Character Creation: https://roll20.net/compendium/dnd5e/BookIndex
Monster Stats: https://roll20.net/compendium/dnd5e/Rules:Monsters%20by%20Name#content
However, D&D is not compatible with PVP, at least, players are likely to use cheese tactics that will cause 1 of 2 players to become enraged.
If it's PVP, you need to have some kind of either ruleset or friendly attitude agreement before you start the game. And then I would go with, state a wager and do /roll 1d20. For example, say, "I attempt to tackle Bob to the floor, 11 or higher /roll1d20" and then you go with the result.
But again, your other players have to agree to the system beforehand in some way. Because if you roll 13 and bob says "heyyy but I have 15 strength so you fail" then you might as well just give up. You have to ensure your partner has your same faith in rules and dice before you start.
A LOT of rpers (bad rpers) are only playing for the infinite power fantasy and while they're not necessarily all bad always, you do want to identify them so they don't mess up a game that's not about an infinite power fantasy.
This is one reason why I play in venues with strict rules and strict moderation.
>Then again, faceclaims cannot be celebrities, models, or found on Pinterest. The most recent strict ad I read stated no celebrities, models, pictures from Google or Pinterest or Tumblr or Instagram ...
Except for the real clincher that you must own the photo, you could just use this: https://thispersondoesnotexist.com/
Unrelated but a good tool for screenshots is lightshot. . I use it, it's super lightweight and gives you the option to save, edit, or quickly upload images in a way that makes it easy to share