Currently, I'm a Vivaldi user. My issue with Vivaldi is simple: it isn't fully open source.

So what are my options? The obvious ones are Brave and Firefox.

But.

Brave has all the crypto crap, its sync feature sucks, as it doesn't even save all my settings, the mobile browser version of it sucks even more, because I couldn't find a way to access tabs from my laptop on the mobile client, and Brave mobile only supports the tab bar at the top (I want it at the bottom, phones are big, at least make them easier to use)

Firefox has the sync features, the mobile version supports tabs at the bottom, and sync is easy and works well, and on top of all that, it is either packaged by or preinstalled on most, if not all Linux distros BUT I have 3 issues with Firefox: Data collection is on by default (not that big of a deal, as it's Mozilla, not Google, the data isn't that much and can be turned off with a single toggle), Something very important for me is small tabs, and Firefox' tabs are MASSIVE. I just want small tabs that look like Brave's tabs, same colours, small and simple. And third, I want a better start page. Firefox' start page doesn't support custom backgrounds, and I want one that does. And preferably also has privacy statistics like number of ads and trackers blocked.

Lastly, it has to be based on Chromium or Gecko (Firefox' engine) so I can use all my browser extensions.

Is there a browser out there that meets all my criteria?