This is how Finder looks with XtraFinder enabled, if I recall the original developer died, and someone took on the project, hopefully an update aligning with macOS 26 design will be available even though the app work just fine, no crash, etc
It is Finder not another finder, it is integrated right into Finder, it looks great with version below macOS 26. The only down side is that you need to disable SIP. In past version you could disable SIP partially after installing it.
As for what it add to Finder, I don't even know where to start, so here is another screenshot of the list of features
The background color is because there is no background color defined on the body (CSS), so macOS just apply that blur which break website, I noticed that on Zen, Safari already
Here is the link so you can dive in yourself and look at the screenshots of each feature
Plus the trial is unlimited, before there was countdown before you could interact with it after a reboot, but it seams like it was removed, also it display how long you've been using after the trial expired.
It was far more useful when I still used Snow Leopard. It added so many basic features that have since been added to the vanilla Finder such as tabs, folders on top when sorting and lots more.
Having to disable SIP for it makes me not want to use it anymore, even though I've paid for it many years ago.