Like the Currie, the Rayos has a lot of torque, independent human and electric drive systems, and a drive system that freewheels when not in use. The electronics shut the motor off at 80% battery discharge to avoid a full discharge (which really shortens the life of lead-acid batteries). The Rayos is an 8-speed bike that uses standard bike parts. Seats, handlebars, brakes and other non-electric parts can be found at a supercenter or bike store. Electric parts can be obtained from Rayos dealers.
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.