I didn't know a mini velo thread existed under the Folding Bike forum.
I've been riding my Sundeal $139 mini velo since 2018 as a errand runner in Brooklyn, NY.

My other mini velo is a $500 Java, more refined than the Sundeal.

Both mini velo are used mostly for shorter distance riding among busy traffic.
The smaller size makes them smaller target to avoid motorized vehicle.
Not particularly well suited for sustained high speed, since the smaller frames/wheels transmit more road shock.
Disc brakes on both mini velo pretty much makes them ideal for pothole ridden city roads.
20x1.5 or 1.75 tires offer good traction and suspension, skinnier tires would likely provide much stiffer ride at high tire pressure.