Im not sure security is safe with tether. This is still untrusted token that claiming to be backed up by usd. I know its commonly used on market but holding it on a secured own wallet would be still the same.

I have usdt and holding it on my own non custodial wallet. I think myetherwallet is enough since usdt is an erc20 token supported. But if you want without fee then hols it on a tron based usdt.