From all I've read, the DJI RC micro SD card size isn't as important as the card size in the Mini 3 Pro drone. Assuming this is true, could I put a large size card in both places and then swap them if the card in the drone becomes full?

You sure can.  

As DowntownRDB says yes you can,  just make sure they are both the correct speed,   anything on the approved list for the drone is fast enough for the controller.  

No difference. Buy two identical so it won't matter.

Yes, you can swap but look for disappointment when you can’t read the files from either. Hopefully this will change in future firmware updates

Yes, you can swap but look for disappointment when you can’t read the files from either. My want list is to be able to put the mini SD card into the RC  as to view videos, delete/transfer to devices. Hopefully this will change in future firmware updates

Hi there. Thank you for reaching out. Yes, you can swap SD cards from your DJI Mini 3 Pro to your DJI RC. Please note that we strongly recommend using a compatible SD card to avoid issues. You may refer to the image below for the list of compatible SD cards for the said unit. Thank you and have a great day!

Mini3Valencia Posted at 6-26 18:29
Yes, you can swap but look for disappointment when you can’t read the files from either. My want list is to be able to put the mini SD card into the RC  as to view videos, delete/transfer to devices. Hopefully this will change in future firmware updates

Hi there. Thank you for reaching out. I will take this as a suggestion of yours and will forward it to our designated team for attention. After the evaluation of the engineers, significant suggestions or requests will be implemented via the firmware update, app update, etc. For any updates, please stay tuned to the latest news on our DJI official website at www.dji.com. Thank you for your understanding and support.