Sounds like you already have a handle on things but I suggest you review this thread if you haven’t already and post a bio profile (11 questions) so we can best answer your questions.
Beginner questions - Support - Xert Community Forum (xertonline.com)
A @wescaine points out your signature will dial in over time from BTE’s (breakthrough events) which can occur organically or be targeted by selecting a BT workout and riding it in slope mode. See tips in the thread above.
“All-out” effort to achieve BT’s is relative. You aren’t required to perform traditional FTP tests (RAMP, 20 min or 2x8) which are a lot harder.
XATA will warn you with a triangle(!) below your training status if your signature becomes stale (no BT’s in over three weeks).
Keep in mind TP isn’t the same as FTP for everyone but lots of users find a close correlation.