A couple of thoughts....
Since Apple debuted their new 2018 iPad two days ago, it's got some fairly serious horsepower and the 32gb wifi model is $329.00 USD, so that's smack in the middle of refurbished money. When I first got my Mavic Pro I used my iPad mini2 with 32 gb and it was fine. Best Buy had a blowout sale on the mini 4 a few months back and that's my go to flight device - no 4G (not interested in movable waypoints), but 128 gb memory. It's never faltered.
Also, I'm not aware of any iPad that has a removable memory card. I'm sure the 4G devices have a simm card, but my iPad 3, both minis, and my wife's 2017 iPad don't have any card slots. Other than using a lightning cable direct to my PC the only other way I've transferred any data from an iPad to a computer was with the double ended thumb drives - USB on one end, lightning connector on the other.
Hope this helps.
Jake