I have two bikes, a DAS-KIT hub drive and a Bosch Mid Drive. Both operate differently, but the power level for the DAS-KIT is hidden in a password protected menu. The PAS on the DAS-KIT always puts out the same power except when close to the max restricted speed, then it fades out. The PAS on the DAS-KIT basically sets the top speed when pedaling. So if I'm riding with a group I set the PAS to match the speed everyone is riding. If alone I typically set it to max PAS, which gets me to about 24mpg with easy pedaling.

The Bosch mid drive is my mountain bike and I usually ride it in EMTB mode. Which scales the percentage of motor input to rider input based on how hard the rider pedals. This gives a very natural feel to the motor. IOW you don't feel it kicking in. It just feels like you are stronger. The other modes like ECO, TOUR, and TURBO add a fixed percentage based on how hard you pedal. Versus the EMTB mode that scales that percentage.