I would consider using a 20-inch wheeled bike, and then buy the Golden Motor Magic Pie 4 in 20-inch. The controller is built into the center of the hubmotor/wheel, so it simplifies the installation and clears up half the clutter.
For a battery, I'd adapt an EGO yard tool 56V battery. I have had an electric mower and weed-wacker from EGO for about 8 years, I have beat the hell out of them, and the battery is still working fine, with about 20% less range. Store batteries at 50%-80% in a cool area (not direct sun) for max life.
You can limit the speed and power with the dashboard.
I typically mow the yard at about 50%-80% fill at the start (per my research). Then I charge to full. Then, I do the weed-wacking and that knocks the charge down to 80% for storing over the week. The electric version of a mower allows me to quietly mow early in the morning, before it gets hot.
Sometimes I charged to full while drinking coffee and checking emails, then mow plus weed-wack to end up at 50%, then store for a week.