An omafiets (and there are excellent electric ones from the likes of Gazelle and Kalkhoff) would be an excellent practical machine, up until the point where you go anywhere near a train.
I'd suggest approaching this problem on two different axes: First, the flavour of electric assist. The higher-end world seems to be consolidating on mid-drive systems from the Shimano and Bosch, but there are plenty of hub motor systems around at the lower end. Different electric assist systems behave very differently in terms of how they deliver power in response to your pedalling: Low-end stuff just senses that the cranks are rotating and applies a set level of power, better systems sense the rider's torque and cadence and apply power proportionally, but with different power curves that affect how it feels to ride. There's no right answer, though it's probably a truism that a cargo bike or tandem (or loaded tourer?) benefits from a sharp kick of acceleration as you start off, while smooth delivery of torque is more important for mountain bikes. How the system behaves around the speed limit is important too - if it sharply cuts the assistance, there's a tendency to oscillate, unless the rider eases off to let the electric assist do more of the work, or rides hard enough to stay above the limit on human power alone. The best way to make an informed decision is to test-ride a variety of systems. It's not too important what type of bike they're attached to.
Then, you can start looking at bikes with your preferred flavour of e-assist. You already know plenty about bikes, just be aware that e-bikes tend to be geared fairly high on the assumption the motor will be doing much of the work, and consider weight distribution. The peril of low-end e-bikes is the use of BSO-grade components to keep the cost down.
