The other thing to consider is that this is a Kickstarter project, so you aren’t directly purchasing from the company, but rather “backing the project” in exchange for a bike. Technically, Stark Drive, or any Kickstarter creator, could cut and run with the money, leaving their backers without legal recourse. In this case though, Stark Drive has already run a successful crowdfunding campaign for their previous bike and demonstrated their ability to deliver, so this is probably at least somewhat safer than a brand new Kickstarter start-up.
Riese & Müller have built their bikes to be masters of bike touring. They are some of the only electric bikes that offer a dual battery setup. This means that you are going to be able to go double the distance without recharging. This capability is truly invaluable during a bike tour. On Bosch motors, this takes you from 500 watt hours to 1000 watt hours. There are not any motors offering that type of battery range.
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.