Are you talking about game modes or genres in general?
Deathmatch is smaller amount of people, set items, in a smaller area with first to X amount of points win.
if you look at something like half life death match , you ran around look for weapons and killed the other players, whats the most different in royal is you die one, last one left standing wins.
I hope this gets chucked out of court I mean really, whats next someone sues everyone else for loot boxes