Honestly, this seems to be one of the better tab counter addons on AMO... I've just been through testing about 15 of them, so I should know.

Unlike many addons on the site, the author has a very good description and screenshots and does not skimp on features.

In fact, the only thing this addon doesn't have that I really wish it did is some way to increase the font size (the *only* tab counter addon I found that has a larger font size was 'Tab Count Icon by lllusion3418' but it doesn't have as many options as this one does). I'm viewing from about 10ft away on a 50" TV set to 1920x1080. From there, TCI's font appears ~ 2x larger than TCP's. I can make both out but only just barely on TCP's.

Overall, a very solid addon. I hope increased font sizes become a thing but due to shortage of addons with this feature, I can only assume that it is difficult to do from WebExtensions. If I wasn't holding out for that or I could get me some robot eyes, then I would have no issue calling it the best one on AMO :-)

FF v89.0.2 on Fedora 33 Cinnamon