I think someone here posted a question re the back tap feture that worked ok on their SE2 not working on their SE3. It was OT from the thread it was posted in and I can't turn it up with search ATM?
I played around with it (selecting double tap, for flashlight on/off) and it works but, boy, is it sensitive and finicky. Tap too hard, too soft, tiny difference in each tap strength, too much or too little time between taps and no go. Have to keep the phone quite still (no moving the phone on to your finger or to meet your finger to tap, must be the finger tapping the phone). Only works from lock screen or home/active screen, will not work from black screen. No settings to adjust any sensitivity. I don't have experience with it on other iPhone models to compare but it sure is WAY less useful vs. moto chop light. At least some android phones that also have back tap have some sensitivity & features adjustment included. Seems to me the phone wants to train the user, learn exactly what I want or no soup for you!
On a positive note I discovered that the iPhone has brightness adjustment for the flashlight, wasn't aware.