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?
Are these wallets saves the private keys in an offline environment (in mobile/desktop) to prevent against hacking attempts online?
All wallets you mentioned are closed source junk hot wallets and I wouldn't trust any of them for any long term storage.
I don't understand why you keep saying long term storage of stable coins, there is no real benefit in doing that and you can only lose if you mess around with various tokens like that.
If you need long term stable coins simply use your own fiat currency, but I am sure most of them will collapse soon with inflation.