Let me share with you this case of a Mavic Air going into trees but not crashing; still it was very close.
Shooting at my company's outdoor event, the MA got without battery at around 1.5 m of altitude, and then the Return To Home program was initiated (RTH altitude = 30m).
This was not a good idea as I was under a lot of trees, I have pressed cancel but still it took some time to react and made 4 attempts to get to the required altitude.
elberti Posted at 7-5 13:17
good call; I guess there is no any formula as all cases are different. Imagine you have lost signal with disabled RTH; you are dying in the air
I have the Mavic Pro.
They don't lose signal
(at least, that never happened to me)
What I was meaning is : I set my rth percentage very very low and make sure I fly back before that happens.