Bike Fridays are very well thought of. Positioning is as per a full size bike. The Bernds is a rare beast and geometry is smaller, particularly at the back. For home grown, you could consider a Circe tandem. Non-folding but small, nevertheless.
Small wheels do not carry the momentum as easily, and will steer slightly quicker. On a tandem, that’s not the best property, but you’ll adjust to it pretty quickly. Slightly less relaxing over linger periods. It’s harder work on the front, because you are balancing the whole bike.
I did ride the Steve Parry tandem Brompton with my son once. It was great, but not something I’d want to spend hours on.
To be honest, how often will you want to move it, and by what means? A simple S&S model that splits in the middle is more than enough for a fast fold into a car. Full S&S to collapse into two suitcases is another (expensive) option.