If you have a US passport and there is a remote chance of international travel in the next 5 years, I would apply for GE. If you do not have a passport, you are not GE-eligible.
The chances of being deselected for Pre-Check on any given departure are not linked to the TTP of which you are a member. So long as you "harmonize" the data on your passport, your GE application, and your air carrier profiles, unless you are flagged for some odd reason or you are simply unlucky, you should see Pre-Check on all travel.
By harmonize, I mean taking the time to use exactly the same name, no extra initials, spaces or anything, so that everything is exactly the same.