I've got the Cube 160TM and it only comes as a 27.5 front and back. I think it's only the 140 that comes as a 29er.
Specwise for the money it's an absolute bargain. It's a heavy old bugger but that's to be expected with the 750wh battery. It's very planted coming down stuff and an absolute hoot going up again.
I wanted a Cube 140 because of the 29", but that was unavailable.
I bought the 160 SL 750wh 27.5", then afterwards realized the 29" would have been a wrong choice for me.
If you look at both review treads of @Rob Rides EMTB you see the minor issues this bike has/had, if you look at my tread you see the list of things you can modify on this wonderful ebike.
I tried that method and it agreed with my preferred method of sitting on a piece of corrugated board and measuring the distance between the centres of the two depressions.
I actually got saddle sores from the 130mm wide saddle on my Focus. I did the test and discovered that my sit bone width was 130mm! No wonder it was causing problems. I bought a 150mm wide saddle and comfort was restored.
The Cube Venec feels like concrete. Only with roadbike cushion clothes it was bearable.
I put the cheap ergofit that came off my E-st900 hardtail, the same width, a lot better.