I understand there will be viral shedding for genital hsv-1 during times of no visible outbreaks and its advised to avoid sex during the rare outbreaks, but what is the rate of transmission during periods of no visible outbreaks?

The frequencies are low for both visible outbreaks and asymptomatic viral shedding for most cases of genital HSV1. Most herpes experts say they have rarely or never seen a case of genital HSV1 that was acquired by intercourse; all new cases are from oral sex. Genital to genital HSV1 transmission appears to be rare. However, there are no data on the actual frequency: low risk but not zero risk.