Are these wallets saves the private keys in an offline environment (in mobile/desktop) to prevent against hacking attempts online?
Since those are non-custodial, the keys aren't stored to their server, just your device (
plus your backup)
Locally but not offline, the encrypted private keys have to be decrypted for a few seconds to make an outgoing transaction (
to sign it).
guarda looks like it supports both usdt and busd. Should I trust guarda for long term savings?
And does trustwallet also supports busd and tether such as guarda?
Both wallets are closed-source so no one can be certain how they manage the private keys.
(
the source code isn't public so no one can audit it if their claims are true)
But I think rat03gopoh's point is if you're considering to store your funds to Binance's exchange,
then at least use their non-custodial wallet so that you're the one who have access to your funds, not Binance.