But then, I almost never have more than 2 or 3 tabs open at a time.

I used to use and love it, but not for a while. I love Opera, but had an issue with it that I can't remember now. I love the feature where you can tile tabs. I do have too many tabs open most the time...but I switch between then and Opera makes it easier to realize what you have open.
Have you ever used Epic? Never heard of Pale Moon...hmmm....Edge?

it's Chrome based, but they claim they took out all the spy stuff.

Edge replaced Internet Explorer and comes with Win 10. It was incomplete when they first brought it out, but it's getting better. It's the default for a lot of things, and I haven't bothered to change that since most of the time it works just fine.

I actually use Edge more than any of my other browsers anymore. Its gotten much better than originally released, especially with the "Creators build" update. Fast , secure ......

While I still have F.F. installed I very rarely use it anymore. Its very slow compared to Edge and "buggy", not to mention the memory it hogs. I don't use Google or Chrome period. Stopped using Opera when it was bought by a Chinese company. Yeah, I know but ..... in fact I'm banishing ALL Chinese owned or developed programs these days. Used it , Opera, for many years but it kind of died a slow death even before the sale. If you like the OLD type Opera (innovative and fast) try Vivaldi its very much like the Opera of your memories.

Ubuntu/Mate 16.04
I have a hold in circuit using a small relay so if we lose power and then get a power surge my electronic components are protected because they're not connected since the power lose dropped the relay out and opened the contacts that I use to power my components. In other words around here it happens quite frequently that we have a blip in our power so the relay drops out, power goes off of my computer and it dies. Once I decide that everything is ok and push the on button again which picks up the relay closing the contacts and restart my computer then I click on Firefox all my open tabs are right there just like they were when the power goes off.

So it must be a problem with your operating system or how you have it set up. Is my guess.

Can't view any site in more than two tabs. Even the second tab is buggy, and trying to open a site in a third tab is a total fail.

I don't have a problem but that might be because I bring it up while holding down "shift" "x". What that does is disables all apps.

this one is spiraling down to the end .

I'm a Linux user. (PCLinuxOS 16 gb AMD 8 core CPU) I mainly use Firefox. It works beautifully. I have 9 Firefox windows open at all times with over a thousand tabs open simultaneously. One of the 9 currently open windows shows 660 tabs open. No other browser equals Firefox's performance in this area. Actual open tab count over all 9 open windows at this moment is 1235.

When closing Firefox I use the Linux keyboard kill switch which is ctrl+alt+esc. That instantly kills the application. When I restart Firefox it returns to exactly where it was before killing it. Nothing lost. Been doing it that way for many years. The actual install date of PCLinuxOS on the system I am using is May 13 2019. PCLinuxOS uses a rolling release style of updating. It basically evolves to the latest version as time goes on.

I use the Brave web browser for its privacy and security features. It works well but suffers from the same poor tab handling most Google Chrome type browsers suffer from. Other than that its a decent web browser.

I occasionally use Google Chrome for some corporate store types of websites. I wouldn't use it as my daily web browser due to its terrible use of system resources. Its a resource hog.

I have access to several other web browsers, including Edge, but I don't use them. (Yes, Microsoft Edge is available in Linux)
Firefox is my main browser. Additionally I have the Adblock Plus, NoScript, and Privacy Badger extensions installed in Firefox. In addition to their obvious features Adblock Plus and NoScript go a long way towards reducing the system resource load on your system by eliminating the ad crap and resource hogging scripts on webpages.

Don't leave home without them.

I'm finding more and more websites that don't play nice with Firefox. My credit union is one of them, had to switch to using Chrome for that website and others.

Firefox needs to fix this, or I'm going over to Chrome full time.