I am not sure. I think that depends on the platform and exchange. I think, in any case, that if you were using 2 different crypto currencies, the possible added exchange rate fees and price uncertainty would overtake the benefit of doing it. I am no expert and I have only traded Bitcoin, so I'll leave the particulars to more tech savvy users. But if you are looking for the simplest, reliable way to pay without it being traced back to you, even if someone has your smartphone with no password protection, then a wallet-to-wallet bitcoin transfer using CashApp or something else as simple to use is your best option.