Not sure how practical this is, but if you get picks with the thicknesses clearly written on the face, you can use these as thickness gauges for adjusting action. I like 1mm ones - I lower the action on my guitar, slip the pick in between the metal 12th fret and the string, and then while in playing position standing up, I raise the action until the pick falls off, meaning the action is around the same as the thickness of the pick.
If you want a more precise BPM setting on your TC Electronic Flashback's audio tapping feature, download yourself a metronome application on your smartphone. With the volume at full on your phone, set your desired tempo, activate audio tapping, and play the clicking tempo sound on your pickups Toneprint beaming style. The pickup will hear the clicking sound, which will then be analysed by the Flashback. Verify the precision by continuing to play the tempo clicks into the pickup while the Flashback repeats the click sounds in perfect time.