The truth is, yes casinos can control a slot machine or rig it only to give players small wins. Some casinos work with developers to create exclusive games. This gives them even more access to a game's code and RNG.
You just have to stick to legal, regulated online casino sites such as BetMGM, Caesars Palace Online Casino, FanDuel, Betway, bet365 and BetRivers. They offer great casino game ranges and they will pay out quickly and without any issues if you win.