The final major consideration is what type of riding you will be doing. Are you going on an off-road adventure through the mountains? You’ll want a very different electric bike than you would need if you’re riding on paved roads the whole time. Most bike tours are going to be on paved roads, but you should always research the area in detail during your planning process.
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.