We got the 6 speed. I find I can ride it surprisingly quickly – not perhaps as quickly or comfortably as my Fairlight Strael, but it works really well.
A Brompton plus an e-bike conversion kit (like https://www.swytchbike.com/p/brompton-ebike-conversion-kit/) would solve any issues with terrain. I have a GoCycle, which is great but doesn’t fold up quite as small as a Brompton.
