Pale Moon plays this game as smooth as silk
That's good to know, although I would add the caveat that it plays smooth as silk for you, but other people's results may vary. I tried it for a while but I had meter problems so I gave it up.
In my opinion there are no browsers that will work well for everyone, because everyone has a different set up on their machine and that seems to be what makes the biggest difference to game play. There are innumerable browsers and innumerable PC (or Apple) setups, and unfortunately I feel that it is just a case for each person to experiment and find out which browser works best for them, on their machine.
For the last year or so I have been using SRWare Iron for example, which is Chromium-based. For me the meter is almost always smooth and I am not having any issues with flash needing to be allowed either. Before that I was using Opera and liked it a lot, but that was one of the earlier casualties of the flash abandonment for me and I haven't been able to use it for game play ever since then.
But I have always had trouble with browsers from the Firefox family, and heaven knows I've tried a bunch of 'em. Lots of people recommend them because they work well for them, but they don't for me.
I have also found all versions of Microsoft browsers (IE, Edge) have been useless for WGT on any computer I've owned, but again I see them recommended from time to time by others around here.
Trial and error (plus some basic common sense computer maintenance when playing) seems to be the way.