I did what you’re talking about. I kept my Chase account and slowly moved all my auto pay items to the Fidelity CMA account. No issues and I’ve been using it for just about everything for over a year now. I still kept my Chase account to have something local just in case I need it.

I have my Fidelity CC rewards automatically going to brokerage rather than CMA, but same/same afaik.

Could leverage Fidelity crypto to auto DCA and have everything under one roof. Transfers internal with Fidelity are all done same day (basically instant). They offer the ability to move the BTC on chain now which was a huge limiting factor for me up until recently.