My biggest concern is that there are so many exchanges. How the heck do I know which ones will pay me after I make an exchange? I know I have to check their reserve balance, but what else should I look for?
what do you mean can pay you? Actually if you created an account in exchanges and you trade, all your profits and entire balance will be displayed in your account, and no one can manage it only you. So it's all up to you if you want to cash out if you want roll your money again.
Btw fyi every exchanges had different fees, and i suggest better to choose a trusted exchange to prevent scam platforms.