"What should you set your betaflight looptime to?" is one of the most common questions I get today. No longer is there one simple answer like there used to be. I'll tell you what you should set your gyro_sync_denom and pid_process_denom to in order to get the best performance for your setup.
PLEASE NOTE: KISS is an F3, not an F1 processor. I have no idea why, but I was sure it was an F1. Maybe all the, "1 kHz is plenty fast enough," talk. Anyway, please accept my sincerest apologies and know that this was an honest mistake and not because of any ill will or intent to disparage KISS in any way.