I use different browsers for different websites / web applications.
For bank or accounting, for example I use Firefox in a container.
I configured Firefox to clear everything on closing : cache, cookies, history.
I don't save the passwords in the browser. I keep them in Vaultwarden, installed locally on a miniserver.
I'm currently trying out LibreWolf. It is based on Firefox, but with extra privacy and security features. I also installed Vivaldi, also if I am not a big fan of all these extra features integrated : mail, calendar and notes.
However, according to my logic using Brave + Firefox simply must cause more data to be collected than using only one of the two, no?