The only thing I know is if you are just getting the post 56 Firefox, and you're figuring out that you'll be doing a bunch of googling and about:configing, and a lot of css editing, don't forget to check if you're in multi-process mode (peek in task manager.)
If you don't, you might end up like me last night - restarting and restarting to see if the css edit would work that time. No it wouldn't, because there's 5 more processes running that you didn't know about, so restarting doesn't do anything in that regard. Feature or bug, I dunno. But annoying as hell.
Maybe it's because Windows is a pretty mature Operating System used worldwide. Whenever there's a problem, chances are very good that it won't be the first time it has been encountered and either solved, worked around, or fixed using an after-market program.
So, instead of asking here first, it could be that members Google, Bing, DuckDuckGo, etc., to find a solution.
I will admit to using my phone for so much these days. I don't find myself using my desktop or even my laptop. How well I remember the days of being here for hours every day with the problems with the early versions of Windows and constantly upgrading the weak hardware we had back then. A lot has changed in 20-odd years.