It's really up to you. When I use the decel feature for a rear-facing light on the bike I set it to pulse so it's really visible.

Hello John. 1. Yes, everything should work in the background 2. Tested this here with an iphone running 17.3.1, and settings are being saved for both temp plus and auto brake. Suggest that after you make a setting, back out to the opening screen before going back to change a setting. Let me know if you are still having issues, but I tied it multiple times and settings are sticking. Dan