Yeah, I'd stay away as well, based on what I discovered. To me they look like a full service hedge fund/brokerage that advertise low margin loans because they make up for it with the rest of their fees.
Last year I sent some of my assets from Vanguard to Interactive Brokers. I think they still have the lowest overall account cost + margin loan cost. But I think Robinhood might offer low margin rates as well, if you want alternatives.