It depends on the age of the property. Less than 5 years old you can get away with 1 per 100 easily, as the property ages and R&M increases, you might need to revisit. Your use of outside vendors also plays a factor in it.
I have 900 units in one town that are spit 60%-40% and are about a 5 minute drive apart. They are staffed 1 per 100, the smaller property is still in lease-up and the other is 10+ years old. The staff from the lease-up help out the older property more often than not, as the lease-up ages I know I'll have to add at least 1 Tech to the team to handle the R&M. We also rely on out-side vendors for 75% of the turn process.
Without vendors I'd be at 1.5 to 1.75 techs per 100.
We've found the 1:100 ratio to be realistic. But of course each situation is a bit different. Our properties are still less than 10 years old, and our techs do not paint, but they do take acre of all appliance repairs. They do about 40% of HVAC repairs, and accompany a contractor on the other 60%. We're in an urban setting, so the techs do very few exterior tasks.