Best exchanges, wallets, etc. for DCA (paycheck and/or bank account), lump sum (ACH and/or wire transfers) during price dips, and both under self-custody in cold storage hardware wallet?

I'm interested in buying and holding BTC long-term (but am also considering BTH as well), I plan on doing all my buying, cold storage transferring, and accounting from my laptop using USB and whatever apps/websites the exchanges and wallets have.

Any reason to use more than one exchange? Like getting past daily limits?

I'm considering among: River, Strike, Swan, or Cash App for DCA but I am open to any feedback.

I'm considering the Trezor Safe 3, but am undecided... I've heard issues with it, Jade, and Ledger.

I want something that doesn't rely on a third-party or even on the exchange or wallet, I want to have full custody and control.

Best method for cold storage transfers and UXTO consolidation?

I want minimal fees and spread.

And I'm not a math/tech guy, I want things to be simple and easy to use.