In my particular game, for core gameplay, I'm just sending the angle and whether the action button is down or up. So I just slapped together a Node.js script to spawn N clients that, according to some simple logic send that input to server. They don't even interpret what server sends back to them, because I'm testing the server-side with them. Bonus is that you can test your algos in extreme circumstances, like send all clients to particular spot on the map, so you can see how it performs with different distributions of locations.

This was invaluable to almost all multiplayer games I did.

Wrt mining/ads, I'm considering to default to mining if I detect ad-blocker, or you're on Chrome + Desktop PC (not laptops).