My "sweet spot" for the commute on the Rover has been about 18-20 MPH at PAS 3, it leaves a safe buffer on the commute and rolls well. I do full throttle it on some of the tighter parts. Besides the bigger motor and battery, the mid-drive Frey has the advantage of gears, so with a similar level of effort on my part, I am rolling 25+ and still have plenty of battery, plus I get up to 35 on the tight parts. Also going through the gears on the Frey is much quicker acceleration.
The speed difference is noticeable, and makes a significant difference on the time my 19 mile commute takes.
My Rover is a 2018 - I have not noticed any drop in power until the very last bar, that takes it down to PAS 1 (like 150 watt on the meter) - and it barely moves.
If you've not ridden a mid drive, the difference with using the gearing is major!