If they do have that internet exchange or swap then conversion to TRX will be the cheapest i suppose.
nope, TRX is still more expensive at 5 TRX fee compared to some other options on betfury.
i think the cheapest would be USDT on ETH or maybe LTC. the withdraw fee on both is less than $0.1 and you can easily swap them elsewhere for whatever coin you want.
You are right. Surprisingly, USDT erc20 is the cheapest, even better than USDT bep20 (BSc). But to counterbalance this, the minimum cashout on that chain (Ethereum) is $25 compared to $1$ for BEP20. If you compare this to stake.com, the minimum amount as well as the transaction fee is quite low for both erc20 and bep20 USDT. Litecoin (LTC) is also good, but recently, it has taken much more time to get the first confirmation. I usually choose USDT bep 20.