I only remember when I built my own batteries, I would get more range at lower volts because at about 40+km/hr you end up pushing wind and range goes way down. So yeah, technically power is power, but it's fun to go 50km/hr if you don't have far to go.

There probably aren't many EVs that can't regulate voltage across motor poles between 0 to +battery pack(or -1/2 to +1/2 pack) voltage...

Did your controller only have one power setting?

Yeah it did. It was fairly burly to begin with and I modified it with a stronger mossfett. This was back in 2007 when ebikes were very fringe. I would get packs of defective DeWalt drill batteries on eBay to harvest the good cells and build my own packs. I spent almost as much time building the bike as I did riding it. Ebikes.ca and endless sphere forums were full of help.