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.
Yes, online slots have created quite a few millionaires over the years. Some games can have progressive jackpots worth millions of dollars and it only takes one lucky spin to win the entire amount.