I am strugling to upload 4k videos. So I'm thinking of getting new one. Which should I use? 128gb or x2 64gb??

I've been using SanDisk Extreme and never had a problem. If you're the cautious person you swap cards with each battery so getting more and smaller ones would be the choice. I use 128 GB and don't swap...

128gb V30 U3  and get a high speed card reader too. Amazon not expensive Card is 32$ CA and reader 20$

The 128gb card advertised with the Mini2 is excellent value from DJI.

I use sandisk extreme. Works great.

Hello there FLY QUADS TV. Good day and thank you for the inquiry. DJI suggest using a recommended microSD card on your DJI drones for compatibility and reliability purposes. The microSD card must have the specifications of Max 256 GBUHS-I Speed Grade 3. I will be posting a list of DJI recommended microSD cards. Thank you.

Thank you(:

I use San Disk Extreme Pro and it works great!