
On my Priority Folder, the seatpost comes in two parts, and as long as you aren’t too tall, you can use the second part of the post to raise the seat enough while still having a foot.
I want to add a seatpost caster to mine so I can roll it folded more easily, but overall I like the design.
I also tend to just fold my handlebars down when I’m at my office desk or when I bring the bike home (I leave it by the door). I only fold the frame when I need to put the bike in the car or something.
No, I don’t really know much about them aside from the fact that they exist. Just make sure it matches your tube’s diameter.