There was a British site selling 2-pedal-hole stoker cranks for wives and kids. There were two sizes. One was like 165/140 mm and one was like 150/125. I can't find it right now though. So that's from memory.

1x tandems can be set up with right side drive using just single cranks. The inner ring position is used for timing and the middle ring is spaced out to the tandem-spec rear chain line. This is more often done on e-bike versions as they don't have any provision for left side rings.

We have a pair of Tandems East crank shorteners and they work... ok. They space out each side a half an inch, though.

Someone will check me but I think all versions of AXS use hydraulic brakes.