You can get a desktop vs mobile report by selecting "Device Type" dimension
"Other" can be used for identifying "desktop" visits.
You can further break this dimension by operating system and browser dimension to get a holistic view of desktop traffic
There is a really cool way to do this but it can get a bit messy with many dimensions selected:
You will need 2 segments(one for view group A and one for B)if you want can use default view vs a segment as well.
First pull a regualr report you want. then at top look for "Compare to segment". Just pick segment # 2 and voila you will get 2 columns comapring to each other. You may need to adjust which segement you view vs which you compare to get the % changes to reflect as you like.