I’ve used Pale Moon for quite a while, it’s compatible with the few add-ons I have from FF: Adblock, https everywhere, and the general java/shockwave/etc extensions.
It strips out most of the bloat that FireFox has added in, and runs much smoother. I usually have 20ish tabs left open, then add another 15-20 when browsing through Drudge/FR.
The only big issue I’ve had with Pale Moon is the stupid Army CAC card for SSD classes, it’s only officially supported on IE 9 on Win7 (or IE8) and it was a fight to get it working between PaleMoon, FF, and IE.
Recently I’ve had issues with some menu stuff/in-game stores in KingdomofLoathing, the site’s right-click interface is being over-written by the generic browser right-click menu, and not letting me click on some buttons.
Otherwise, PM is great and I’ve definitely liked it better than FireFox or the all-seeing eye of Chrome.
I don’t do games but you could try Nuke Anything Enhanced 1.1 https://addons.mozilla.org/en-US/firefox/addon/nuke-anything-enhanced/?src=api