Hi MingHenry. Crypto is something I'm just not interested in learning the ins and outs of.
So, when purchasing from QSC, I arrange a simple ACH wire transfer from my bank (BofA) that is deposited directly into QSC's bank (Citibank).
It's a nice, stodgy, old-school, trackable financial transaction. Only downside (though not for me; it didn't matter) is that it can take one day or several. Because I chose "ACH" wire transfer option, it was fee-free. I could have chosen "International Wire Transfer" to have it delivered instantly, but there was a fee.
There may be reasons to not buy from QSC, lol -- but just know that the payment method doesn't have to be one of them