As for tab-heavy users, I find FF Quantum to be horrible in this respect, and I keep missing Chrome, which allows a ton of tabs and resizes them, albeit slightly unreadable after ~40-70 tabs, but at least I can see the icon, which is usually enough to find what I'm looking for. FF resizes until ~5 characters of the title are still visible, thereafter requiring "< >" arrows to scroll through tabs... unfortunately if you click one of those arrows too fast (twice in < 1 second), it will skip 10-20 tabs or jump to the completely opposite end(!), which can be frustrating to get back to the tab that is just barely hidden off-screen. I have seen this complaint in forums but still haven't found a reliable workaround other than editing some javascript relating to the default theme (I forget the details)? I have reverted back to tab/ctrl-tab to cycle through tabs.
I use Tree Style Tabs.
It's a pity firefox still doesn't support it properly by allowing the top tabs bar to be hidden without userChrome.css hacking. I just ignore the top ones for now.
Regarding Tree-Style Tabs... I wish I could agree with you, I have been trying various Tree-Style Tab plugins on multiple occasions over the years, often for months at a time... before always giving up out of frustration and resorting back to tabs on top. I honestly can't tell you the exact reasons, but it's generally a frustrating experience... initial transition takes a couple days, plus issues like lack of proper hotkey support e.g. tab/ctrl-tab for tab switching, ctrl-f4 to close a tab, ctrl-t to open a new tab, some or all of those hotkeys tend to not work properly. Multi-screen support was also... lacking, for lack of a better description. There were various other minor annoyances and quirks with every plugin... and I tried various plugins for FF and Chrome before ditching all of them. I will probably try again soon, now that FF Quantum has been out for awhile, hopefully more plugins have been created.
I'd never heard of this, so I thought I'd give it a go: it's not on the right-click menu but on a separate icon on the top left, where the System menu should be so I'd never looked there. It turns out to be handicapped by not being able to save/restore individual tabs, you can only push all of them off and then restore ones you want.
Edge is rather hostile to tab-heavy users in other respects - it doesn't restore them after close, and it just makes them smaller and smaller without any kind of scrolling. So beyond about 20 tabs it becomes hard to use, and you'd never reach 200.