SSD or RAM upgrade?

Moved from the Premiere Pro forum to the Video Hardware forum.

In your case, going from a 64GB to 128GB RAM will likely have a bigger impact on performance and workflow when editing 4K h.265 footage in Premiere Pro and After Effects. If the tasks involve large data sets that require a lot of memory→RAM. With more RAM, the system can store and access more data in memory, reducing the need to swap data in and out from slower storage devices.
If the tasks involve reading and writing large files frequently, such as video editing or data processing→SSD. The faster SSD reduces load times and improves overall system responsiveness.

That's a good question. If that would be an internal Nvme drive, I'd go for that for all cache files.