If OP is still reading...
I don't know how much exercise you want, but a strong rider can sustain ~250 watts on a commute. If you get a 500+++ powered bike, it will be a lot stronger than you. You can of course work as hard as you want, but roughly speaking, above 20mph, you are not really helping much - so you can do as much or little work as you want. Alternatively, many people "dial down" the assist if they want exersize. Others of course find the "turbo" mode so much fun, its hard to dial it down.
I'm certainly way off "normal" for an ebike rider, but I put out a lot more power (through my legs) when I am on an ebike than when I am on a non e-bike. But, if I could teach myself to relax, I could get to work without a sweat if I wanted.