[Zubersoft]

The 1st and 2nd gen iPad Pros should work just fine with MobileSheets. The 2nd through 6th gen models have a 120 hz screen, so writing with the stylus will be a little smoother. About the only advantage specific to the 6th gen is that the stylus supports hovering, so you can enter the annotation editor without even having to put the stylus against the screen. You can read about the different models to see what matters to you: https://en.wikipedia.org/wiki/IPad_Pro

Obviously the newer models are a little faster, but it may not matter if you only plan to use MobileSheets.

Mike