Can I use an iPad Pro Wifi only version or will I need the Pad Pro Wifi + Cellular version to be able to use DJI GO 4 app (with Mavic Air)?  Thanks for clarifying!

wifi or wifi + cellular will both work.

Good day! You can see in this link what mobile devices are compatible with Mavic Air: https://www.dji.com/mavic-air/info#downloads

up2you that is

The only difference between the 2 other than cellular obviously are the WiFi only does not have GPS where the Cellular version has GPS built in.  With the cellular version you'll still have internet and GPS for maps and data depending on cell service coverage for the area you are flying in.  I fly off a regular WiFi version and either tether data from my cell or a hotspot for my maps and data.  When I am flying from my house I still have Wifi access so I get updates and maps either way when I am flying from home or the field.  Personally for me I can't see paying the extra money for the cellular version and a data plan when I already have it on the phone that's sitting in my pocket.