I am about two weeks ahead of you on a similar search.
This is a great forum, but the experienced guys forget we do not understand many acronyms they use. Try to read between the lines.
What I have learned so far is there is no perfect e bike for everybody, but there is a perfect one for YOU. You must decide what you want.
For simple riding around, I prefer sitting in an upright position, so a Cruiser style is my choice. Others like to go faster and enjoy sore backs from leaning over the handle bars.
Folding bikes are great if you use it for commuting or around campus and want to carry them into an office or apartment, or transport in a car trunk.
Fat tires - 4" wide - are great for trail riding, riding in sand, mud and snow. Thinner tires - about 2" - are fine on pavement and other solid surfaces. They are obviously thinner and are easier to pedal.
There are 3 basic motor positions. Front hub is easy to add to an existing bike, but "pulls" the bike instead of pushing, like pedals do. They are rarely found on a new bike.
Rear hub are similar, but the weight is behind you, not in front. It pushes the bike and feels more normal. They are found on most lower priced e bikes.
A mid motor actually powers the pedal crank. The weight is in the center and uses whatever gearing the bike has. This can give faster starts and higher top speed. It also applies extra wear to the crank and chain assemblies. Most higher end bikes are mid motor.
Within each motor location come geared and gearless hubs. In gearless motors, the hub turns at the speed of the motor. Geared hubs have internal planetary gears, so the motor may make 5 revolutions for each hub revolution. This is easier on the motor and likely will increase efficiency a bit. Also, geared motors will "free wheel". Think coasting down a hill or pedaling normally with no motor resistance. Many gearless motors do not free wheel, and will slow you down when coasting. When pedaling without power, you must also turn the motor. Some can take this drag and recharge the battery a little bit - regenerative motors.
Power assist comes in 2 basic forms. PAS or Pedal ASsist will kick in when turned on AND you pedal. Different controllers offer different numbers of assist levels, from 3 to 9, that I have seen. You stop pedaling, assist stops.
The second is throttle assist. There is either a ½ turn handle grip throttle or a thumb operated throttle. In this mode, no pedaling is required.
You may also use both at the same time on many bikes.
Some claim 3 modes. The third is pedal power with no assist.
One possible issue is batteries. Known name brands are fine, but some no name Chinese imports may not hold up well.
The power a battery can deliver is Volts X Ah, minus 20% A 36V 10Ah battery contains 360 Wh or watt hours. However, you can not use more than 80% - 90% of that power without doing permanent damage to the batteries.
The motor wattage - 250W, 350W, 500W, etc is a gross measure of the power output of the motor, or how quickly it will get you up to speed. For casual riders, especially light weight riders, 250W is probably enough. For die hard speed demons, 1000W may not be enough!
There are also legal limits to speed. Class 2 e bikes are limited to 20 mph, I think, and Class 3 limited to 25 mph. In the US, anything over 25 mph and it is no longer considered a bicycle, and it must be licensed and insured. Almost any e bike can go faster than this, but is limited by controller settings.
There are also significant differences in the display.
Prices depend on what options you want. Low end complete bikes start at about $600. Good quality, name brand e bikes start around $2000. Higher end models run $5000 and higher.