There are still a few "quirks" with the way a few websites display, but I've noticed that with nearly ALL the browsers on the market today.
Here are the browser extensions I currently use to add functionality...
1. Ublock Origin : The best of all the ad blockers IMO. I never blocked ads until around four years ago, when a rogue banner ad tried to throw malware at me. Luckily my antivirus caught it before any harm was done.
3. User-Agent Switcher : Handy for spoofing the browser user agent string for websites that are looking for a more "major" browser.
4. ScrollToTop : Toolbar button to scroll immediately to the top of a page.
5. Open Image In New Tab : Adds a context menu item to open images in a new tab.
6. Mute Tab : Extension to keep websites that might have autoplaying audio quiet until you are ready to hear them.
7. AdBlocker for YouTube : Keeps most pre-roll ads on YouTube from playing.
8. Forecastfox (fix version) : Handy weather extension for the URL bar.
9. Cookie AutoDelete : Adds cookie control functionality that isn't built in to any browser that I'm aware of.
10. Black New Tab : Use a black page as your new tab page.
11. Webcompat.com Reporter : Handy for reporting websites who aren't using standards and only want you to use one of the few "major" browsers.
12. Share on Twitter : Share current tab, links and selected text on Twitter.
13. Share to Facebook : Share Button for Facebook lets you share your web page on your Facebook timeline by adding a special Facebook Button.
browser.cache.disk.enable - false
browser.sessionstore.interval - 864000000 (to keep the SSD in my PC from getting overwritten too many times)
media.autoplay.default - 5
media.autoplay.blocking_policy - 2
media.block-autoplay-until-in-foreground - false
media.autoplay.allow-muted - false
media.autoplay.block-event.enabled - true
privacy.purge_trackers.enabled - false