Thanks for your feedback! It's "plus" because it solves the performance and flickering problems that I encountered in other tab counters. I had to implement some new WebExtension features in order to do so, or rely on some non-trivial (and not completely perfect) tricks for older versions.

For version 3.0 I'm working on a refactorization of the code that handles preferences. After this I plan to add more customization options, see for example https://github.com/Loirooriol/tab-counter-plus/issues/13