Verizon s10+ here.. i have mine set to LTE/CDMA .. as far as I can remember that was always the most optimum so that's what I do.. i haven't read anything suggesting global is the new standard.
my experience has been similar. so I'm trying to learn the correct tap speed.. it seems to work better when I tap a little slower and use the full pad of my finger
you for sure have an app that's rogue or defective device.. install GSam battery.. it might help find the culprit.. don't give up on the phone, I got 9 hours sot yesterday.