Any folding 20” bike would be a good choice. I have a space-frame Moulton which is a wonderful touring machine, and a fast commuter. Its dual suspension system makes it smooth, the long wheelbase and geometry make it steady, and easy to mount racks and panniers. However, it isn’t an inexpensive bike.
I also have a Japanese Brompton clone which I bought for my wife. It’s as good as the genuine article (if not better), but one-third the price. Bromptons are hard to beat as commuters, and I am surprised to see that people have been using them as serious touring machines. My wife likes the Brompton because it’s small, easy to ride, and is accessorizable. The bike came with an external 5 speed cassette, which is lighter and easier to adjust and maintain than the internal hub versions.