I’ve always been a fan of “just barely electric” e-bikes—unobtrusive machines that are 90% bicycle, 10% extra power to conquer the occasional hill—but riding the Mod Easy 3 made me rethink everything.

Ten years ago, if you had told me that I’d be riding what I would soon call an “excellent commuter e-bike” despite it weighing 118 pounds (53.5 kg) and rolling on 24×4.0-inch fat tires, I probably ...