As far as range goes, I’ll typically set the assist levels for the planned elevation gain of my ride and the results have been pretty consistent. 80Kg rider weight: 100W assist gives me 1250m, 125W/1100m, 150W/1000m, 225W/800m, 300W/650m all with a few % battery to spare. I set the % assistance so that I need to be applying about 240W of my own power before achieving the maximum Wattage for each mode. That’s for single track riding with moderate amounts of roots and rocks. Fire roads will generally get about 20% higher results due to more consistent grades and cadence.
I did pick up a range extender after a year for the lazier or bigger mountain days. It consistently gets 400m at 225W, and is usually drained by the end of the first climb leg, so just goes into the backpack for the rest of the ride. Don’t really notice it at all there, as its weight is mostly offset by the weight of the water I’ve been drinking along the way.