I'm not the best guy to advise you as far as complete bikes. I build from components myself, so I can just tell you what kind of components to look for.

For your application I would suggest getting a bike with either a 200 to 350 watt (250 watt most common size) geared rear hub motor or a 500 watt direct drive rear hub motor. If you like to pedal and are used to pedaling bikes then lean towards a geared hub motor, if you don't like to pedal and/or aren't used to doing so then lean towards a direct drive hub motor.

I can't really advise you as to which folding bike frame to lean towards since I don't have very much experience with folders.

So basically the way I can help you is to let you know what kind of motor to be looking for (see above) you don't need a whole lot of power for your application since you are small/light and you don't have any hill climbing needs. So your looking for the smaller size hub motors (good for light weight both because the motor itself isn't as heavy and because you don't need a very big battery pack which is where the real weight savings can be). To my mind the main decision you will have is whether to go with a small internally geared down rear hub motor (usually 250 watt size but can be slightly more or less) or with the smallest normal size of direct drive rear hub motor (500 watts). The internally geared down hub motors are good for people who like to pedal because they don't have any drag to them when pedaling only but they have a limited service life of about 2-3 years for a person who uses them for a moderate daily commute before they wear out and need to be replaced (gears and internal freewheel wear out). A direct drive is more suited for a person who rarely going to pedal only without using the motor since if the motor is off and you are just pedaling there is a noticeable drag to them. They are also usually more powerful and thus more suited for someone who isn't going to pedal very much and add their power to the equation and they can have a very long service life because there is no internal gears or freewheel to wear out.

From what I have seen of the folder e-bike market most folding e-bikes use an internal geared hub motor (200 to 350 watts but most common is 250 watt) but I have seen a few that do use a 500-watt direct drive rear hub motors as well so you might have to look a little harder if that is the option you want to go with but they are out there. For a folder which is built for light weight with a small frame and has a hinge in the middle of the frame that already gets a lot of stress as it is I would be extremely hesitant to buy one with the hub motor in the front wheel and I personally would very strongly lean towards one with the hub motor in the rear wheel.