Consequences of using a non-privacy-focused browser

Recently, I received a key to test the Arc Browser on Windows; however, as far as I’m aware, it is a browser very similar to Vivaldi, focusing on productivity and a number of features instead of privacy. It’s also worth noting that, because it’s a beta, I would need to log in to the browser with my email.
I really liked the browser from what I’ve seen on other people’s MacBooks, but I’m wondering what the consequences would be of using it as my main browser. The only solution to mitigate any potential shortcomings would be for me to use Arc with websites that already have some kind of ties to me, such as social networks and work-related sites (like GitHub), and use everything else on librewolf or mullvad.
I’m also aware of extensions like JShelter that can attempt to harden Chromium, but I’ve never heard anyone in privacy circles discuss its effectiveness.
I understand that the answers will depend on the threat model, but I can only evaluate it if I know the ramifications of using such an important tool in a privacy-lax environment.