Your stablecoin will be regulated like cash, it will be as safe as cash. You'll get taxed on it like cash is my guess.
They couldn't have defi stable dollars they don't control, that's why I believe BIG money crippled LUNA George Soros style, and will continue to do it to any eco-system that tries to avoid paying the money men.

If you want to trade you'll have to do it in btc pairings and not convert to stable unless you want to declare it I guess. I'm not in the US, I've no idea how it will work. In the UK they are talking of accepting stablecoins as payment, it's not any stablecoin though.