Interesting that a high end NVME SSD with heatsink outperforms the internal SSD slightly in Ratchet and Clank, not to mention BC titles. Also interesting is that at least with the Samsung NVME drive, there is some drive throttling if there isn't a heatsink to help dissipate the heat from the drive as indicated by the heatsink versus no heatsink loading times.
With the Samsung drive, the advantage with heatsink is relatively minor, but I wonder if higher speed drives in the future will afford much better performance than the internal drive. That means that if you have a fast enough NVME drive, then install all your games to that drive instead of the internal to save wear and tear on the non-replaceable internal drive which should help extend the life of the console.
Regards,
SB