I've started using Mullvad Browser recently(switched from Brave) and really like it.
I turn on browser history when using it and was wondering if this would be kind of defeating the point? Obviously I'd get the other security benefits from the hardening done, but should I just use vanilla Firefox?
how many people have access to your account or root access?
How many people have access to the device under a different account?
Are you concerned about cyber attacks?
Are concerned about the device getting confiscated/stolen by another party?
If the answers to these questions are low risk then you basically have very little problems with keeping history on your device. Remember your isp/VPN will be able to see DNS calls and ip address connections which best case scenario will expose the websites you go to.
If having browser history on helps you use it, I think it shouldn't be a huge issue.
I have been using mullvad browser the way I use Firefox focus on the phone. Quick searches for stuff or just browsing casually.
I have a separate Firefox browser for personal stuff.
I use Mullvad as a sort of incognito tab while using Firefox for most normal stuff. I don't think there would be any issue with using Mullvad with history, but there is not much point for services where you reveal your identity by logging in anyway unless you make sure your login is not connected to you.