First I thought you might want a 20" folding electric bike, but those are mostly 7 speeds. Are you interested in the 26" folding e-bikes mainly seen on Amaxon for around $600-700?

Nonetheless, there a quite a few 20" folding bikes with electric assist. I would say most are probably 45 pounds and up. I don't know that this is easy to roll, but probably a hefty load to carry. I think you can expect these bikes to have a range of 20-26 miles and a top speed around 18 mph whether you pedal them unassisted or use the motor.

I am an ebike hobbyist the past 4 summers, and discovered folders two years ago. We have a Downtube Nova and 8FS, where I added rear hub motor kits and a small battery. The conversions were $500-600. Half of that is battery,, The bikes were $300 and $400. I could have bought low cost electric folders for less, but I wanted to have starter bikes that were known for quality and this forum appears to think they do. They weigh 35 and 39 pounds. 18 mph and about 25 mile range. We use them for riding around on bike paths. Only folded if they go inside a minivan.

If you want a good fold and have the budget, you probably cannot go wrong with a Brompton. They offer a front drive kit and so does Grin technologies in Vancouver. Lots of money.