Best servers for multiplayer?

Depends on the kind of gamemode you like. Hypixel has pretty much everything, but there are a lot of cheaters in the game that don't get banned immediately. If you're into UHC or PvP type games, then you might be interested in Invaded Lands, Mineman Club, Velt PvP, Arcane, Faithful, Arctic UHC, etc.

Just google the name of the server and the server IP should pop up.