I think after all Duels & FFA is the most you learn of in PvP but I prefer FFA for PVP skills. You have more abilities and you can use the build heights, in Duels you can't really. In FFA it's more about tactic which you can use in SkyWars, EggWars, Lucky Islands or whatever you can play. In Duels it's kinda flat and I don't really see that always back in maps, sure you have places with enough of PvP but you aren't used with the kits and space. For example, EggWars OP fights, you need new armor every 3 minutes to continue and you have to eat a lot of Golden Apples.