FAP Security Profiles and ARRP

How good has ARRP been in your experience? I know any form of auto selection is generally viewed as bad but for a small branch office using limited wifi, ('ve found it's generally "good enough" with other access points I've used.

When ARRP re-scans to make new channel selections, does it cause a disruption in service for connected clients? Would it be wise to set ARRP re-scan interval to a fixed time of day when no clients would be connected, or is it OK to do frequent re-scanning with active clients?

I am have a FAP-221E managed by a FGT and the GUI shows me option under WiFi & Switch Controller for "Security Profile Groups". I can then set this groups on any SSID that is set to bridge mode.   Given that this is not an S series AP, what would setting a security profile on a bridge-mode SSID do and why would you want to do it (again on a non-S series AP) vs doing it in policies section of the FGT?