Aosom is just an amazon brand. they sell bike trailers, and one of the cheap motor kit versions.
RE the cheap kit. do get a spoke wrench, and keep your spokes snug but not over tight. The cheaper wheels will loosen a lot in the first 50 miles, and may need some tuning fairly often for some time.
The kit you linked to has a modern display, it should have the ability to choose power levels, so you can set it to level 4 and be closer to legal, but not crazy slow. Use the lower levels as needed to extend range on the longer rides, by not having more than 15 mph.
WM will ship to store any bike you choose from the website, free. So you can get the cruiser with the welded on rack and 7 speeds. That rack will hold up the whole world, without buckling. You will be able to use all 7 gears no problem, but I predict you will put it in high gear, and leave it there. this is why a high quality shifter really does not matter for the e bike.
Ride right, and the cops won't even talk to you, and no worries. Unless you are famous with em, then you are screwed, as I was for about a decade. I had to learn to drive perfect, or else.
Just clown pedal when you see cops, and if you are cruising about 20-22 mph, they won't pay much attention in most towns. Ride the right side, stay off sidewalks if that is illegal for bikes, actually stop at signs and lights, and you won't attract the cops. Just don't ride like 90% of bike riders, and the cops will think you are great.
I also find it helps to look right. What's that? Helmet, yellow shirt, etc. Look like you have money, and a lawyer. Like you choose to bike, not have to. Not like stoner, or bum with DUIs. Why? Its not for cops. Its for cars. Look poor and they will flick your ear with the mirror. Look money, and they give you space.