I find "^history search" to be actually and annoyingly useless because Firefox, like Chrome and seemingly every other browser, has unreliable, short-living browsing history. The times where I find myself trying to use the "^-search" in Firefox are always just a little bit after whatever I was searching for fell out of history retention window. The annoyance part is that my every failed attempt at using "^-search" is another reminder that browser vendors seem to want to get rid of browsing history entirely.
The rest of those tools, they work for me. Sometimes. "%tab-search" and "#title-search" seem to be negatively affected by what the article describes as "some sort of smart guess on what you type there", and overall I had them fail to find the exact tab/page I had open enough times, that I don't trust them.
"+tag search" - that's a new one for me, I didn't know it existed. I only recently discovered you can add tags to bookmarks, and those tags do complete for "unqualified" queries (i.e. just starting to type in the address bar) with some priority, and are displayed nicely.