The Nuvinci hub system is the best geared hub that I have ever used. There is literally no maintenance to be done on this drivetrain. I’d recommend buying it with the Gates Carbon belt because you’ll never run into issues like the chain falling off. You operate the Nuvinci system with a grip shifter and can of course shift even when you’re not moving.
E-bikes mostly use motors and battery options from a few major suppliers: Bosch, Yamaha, Shimano, and Brose. A few other brands exist, but are less reliable or powerful. Some, like the Yamaha system, have more torque and others are quieter. But generally all four make good options. Look for motor output (in watts) which will give you an idea of total power. But watt hours (Wh) is perhaps a better figure to use—it takes into account battery output and life to give a truer reflection of power.