I've spent a long time with folding bikes over the years. My advice: bite the bullet and buy a Brompton[1].
Yes, Bromptons are expensive. But they ride like a bicycle, have gears, a stiff enough frame, luggage racks etc. There's very little compromise. The fastest I've done on mine is 45 kph and I've ridden 70km in a day. I carry it on and off buses and trains multiple times a day without issue.
In the past I had an A-bike[2]. It's a fun and cute little design but the wheels are absolutely tiny and has no gears. You feel like you're riding a folding contraption rather than a bicycle. The build quality was rather plasticky too. I like the idea of an A-shape with telescoping tubes. It's quite an ingenious fold.
I've also ridden (but not owned) a Pacific CarryMe[3]. The ride experience again suffers for the short wheels and no gears, but it could be useful for some. The fold still leaves you with quite a long package.
I'd love to try the Kwiggle bike. I don't think the strange seat will cause as many problems as people think, but I suspect the overall ride experience to be a bit bouncy and flexy. Maybe it's worth it for the small fold.
For a more out-there design I think the Halbrad/Half-Bike[4] could be quite nice but it never really got past the prototype stage. Under-seat steering is a bit of an adjustment too.
[1] https://www.brompton.com/
[2] https://en.wikipedia.org/wiki/A-bike
[3] https://pacificcarryme.com/
[4] https://www.youtube.com/watch?v=TQIC138vmlE