Is Futu (moomoo) safe?

If you're afraid of margin, just double check every time you make a purchase that you have enough cash to make the purchase. By doing so, you'll never end up using the margin.

(I know that's a bit troublesome so) Alternatively, just use Tiger Brokers instead! The comms on moomoo, while cheaper, they do charge a platform fee which in the long run will probably cost more.