My plan was to send Bitcoin to Coinbase (self custody) wallet and ALTs to Trustwallet to diversify risk.
I noticed you mentioned Coinbase Wallet and Trust wallet, soooo are we talking about mobile wallets here? Electrum is the holy grail bitcoin software wallet for PC but last time I tried their android app, it's uh, too basic. I suggest you look into Blue Wallet instead if the situation is still the same. For ALTs there is also Unstoppable Wallet. Afaik both are open-source as well.
But op, if we're talking about decent amount of money here and/or storing for long term, you're better off looking into hardware wallets instead since they're not hot wallets hence you'll be minimizing a great amount of risk, see: Open Source Hardware Wallets