The new MultiplayerSynchronizer and MultiplayerSpawner nodes in Godot 4 (still in alpha, beta soon) make life so much easier. I'm going to be submitting a demo for using them hopefully next week - but generally you just check some boxes for properties to be synced at spawn or continuously and set the network authority for each of them (aka Player 2 is master of his object, but Player 1 is master of the rest of the world) and it does the rest.