In your case, your minimum run time may be dictated by your SWG and getting enough chlorine in the pool. That is first priority. But that may not enough to keep the pool as clean as you would like so you need to experiment some. Beyond chlorination, run time is about skimming, filtering and cleaning the water and pool which is basically aesthetics and mostly a personal choice. So if you don't mind having a slightly dirty pool, you can reduce run time as much as you like as long as the pool is getting enough chlorine.

A variable speed pump tends to have the most efficiency GPM per watt around 1000 RPM. So if you are interested in saving energy, set the RPM to 1000 and see how well the skimmers work and how long you need to run the pump. But don't forget to adjust the SWG when shortening run time.