Why don't you just use all of them?
What you need a stable coin that used the scalable platform. BUSD and USDT TRC20 is scalable enough because each transaction needs only a few cents as the transaction fees.
You can also use DAI that based on the BSD or polygon.
He can sure use all of the available Stable coins on the market and even though there is a fee for a particular stable coin I think it will not hit that hard like ERC-20 did, in my opinion, USDT, is the most notable stable coin that is mostly used for trading, gambling, and transfer because of its small fees and notable name, while XRP is well known aswell number 6 spot next to USDT, and mostly this is the stable coin I mostly used when transferring my funds to Binance, stake.com, and other apps I used when making transactions.