General discussion, compatibility and contributed extensions.
Agreed - take a look through those available and road test those that appear useful to you.
Personally I'm a very heavy web user, sometimes for web site design and testing, so I've accumulated and use a very large number of extensions - but only because I find them helpful. The only one I really couldn't imagine being without is Tab Utilities Phoenix as I've been using vertical tabs since about 2002 - but most people seem to find regular horizontal tabs perfectly fine.
My addons would focus on privacy and convenience. I believe I've installed Decentraleyes, Privacy Badger, Cookie Exterminator and uBlock but the only extension showing up on the menu bar is uBlock. Is this normal?
Is there a "favoured set of extensions"? The ones I like are based on privacy and security, control, convenience, information. Back when I was using Firefox, I used to see lists of extensions posted by different people. If I looked at two lists, and compared them with mine, thee would be very little in common among them, the only exception being the ad-blocker.
The problem with any kind of "favored set" is that, as you've already noted, everyone's favorites will be different based on everyone's different needs and different preferences. And The Powers That Be will not produce any kind of "official" favored set because they are doing their best to eliminate any and all kinds of favoritism and/or bias in relation to extensions published on the PM addons site.
In my own case, I run with a minimal number of extensions -- an ad-blocker, Pale Moon Commander, and another handful that provide various conveniences to me. That's it.
In some cases, you'll have to add the extension icons to your menu bar manually.
If you right-click somewhere on the menu bar, and choose "Customize", then you'll be able to move, add or remove objects, simply by dragging them into place.