Feel free to play with those numbers and make it how you’d like, figure out what works for you! Even something like 400m to spawn and 500 to despawn will still be much better than all actors being spawned at all times! 
That solely depends on what you set your players’ object channel as under their collision!
I will say: for MOST projects, yes. If you use a custom object channel for your player, you’ll want to use that.
Vehicle you may as well tell to not overlap, because it’s still only going to look for children of “Ally”, which I assume a vehicle will not be. IF the vehicle would be a child of that then sure, use vehicle for overlap as well.
Otherwise, someone could leave a vehicle somewhere to keep actors alive and bog down the server.