Lately I bought Ledger Nano X. I want to save my coins in it.
Great! if you're able to gain your hardware issue but just don't get into the recovery option and feature of that, okay?
Which network is safer for holding USDT in Ledger ? ERC20 or TRC20 ?
Both are fine but if you are saving some fees, TRC20 is the option. That's the advantage of going into TRC20 because of the cheaper network fees than the ERC20.