FF has never been my favourite browser. It was my main one, between about 2003-2007 (couldn't get away from Internet Exploder quick enough!), but when Chrome first appeared on the scene I switched immediately, because FF had developed an alarming habit of crashing whenever it felt like it...
I used to use Google's Sync across all my Chrome installs. Then I thought what a very silly idea that was.......installing the same browser, over and over again, in distro after distro. In real terms, it wasted so much disk space; and that was the main, driving factor behind development of the 'portable' browser concept for Puppy. Fredx181 developed the concept first with his portable Firefox, making use of a modified version of a script that had floating around the web for a long time. I then did the same for Pale Moon & Thunderbird.....and then we turned our attention to the Chromium-based browsers. (Which took a wee bit more figuring out, but.....we got there in the end!)
Now, for each different browser, I share ONE browser install across multiple Puppies. The profile remains within the portable directory.....and my data stays LOCAL. I've been with Google too many years to remain blind to what they do with it!
If Sync works for you - and you're happy with the results - use it. You certainly don't need to justify yourself to anybody else.
As to which browser? Gawd. How long's a piece of string..?
There's a ton of them out there. There IS no one "best browser"; as with so much of this stuff, it's all down to personal choice.....do you like the way it looks, do you like the available functions, do you like the way it lets you do things....etc, etc.
You have to try them for yourself. It's not the sort of thing you can get an answer for on a forum, because you'll get as many different opinions as there are browsers. And that's the truth.