I have the same Mac and problem. I used OWC parts to make a 16 TB m2 SSD array that connects over Thunderbolt. It's fast enough to edit 8K footage, just like t

I have the same Mac and problem. I used OWC parts to make a 16 TB m2 SSD array that connects over Thunderbolt. It's fast enough to edit 8K footage, just like the internal disk. Look for the 4-bay Thunderbolt enclosure on Amazon. I did add extra cooling (heatsinks on the modules, and a bigger fan). Total cost was about $2000.