The Dash is an excellent, low-cost option for those looking for an intro to e-bikes kind of ride. The TranzX motor will take you up to 28mph for about 16-35 miles per charge–more if you’re conservative with the assist. The components aren’t too shabby either. Shimano M365 hydraulic disc brakes keep you safe, the Shimano Deore SGS drivetrain, and RockShox Paragon fork with 65mm of travel make it a great entry level option.
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.