Ok, my suggestion is to first uninstall the TBM, then delete all TBM folders in your Aircraft/X-Aviation folder. But only delete the folders AFTER uninstalling. You should definitely not have 2 TBM folders, then reinstall a fresh TBM.
Next, you are perfectly safe to install as many copies of X-Plane as you wish on the same PC. I have 3 on my machine. But keep this one as a testing installation of sorts, as long as you have the HDD space. As long as you don't install any other scenery or aircraft into it, you'll be fine. I'm not sure how other developers DRM works, but seeing as a bare X-Plane installation would only be used as a testing platform, it wouldn't matter.
Of course, this is all up to you whether you want to go down this road, but keep in mind, it will help, not just us, but many other developers, in diagnosing potential problems, as many problems arise from plugin conflicts.