Get a large. With a medium, you’ll feel on top of the bike. With a large you’ll feel in the bike. It’ll be more stable and you’ll learn to make it more responsive in the corners. It’s a light bike. So, that shouldn’t be difficult. If you find it slightly long. Put a shorter stem on it. A 5mm...
This isn’t true with today’s battery technology. You can take them to 0% and it doesn’t hurt them. In fact some companies recommend fully discharging the battery on the first use.
That’s a nice bike. I bought a Trek EXe and I love it for all the same reasons. I didn’t even want an Ebike, till the EXe came out. Make sure your seatpost clamp isn’t to tight. I had the same problem with mine and that was causing it. Hit me up if you ever come down to the Thousand Oaks area.