Storage Configuration with SSD and HDD

Hi there,

I currently went down the rabbit hole of setting up my ideal storage configuration with Immich on TrueNas. So far I'm quite happy with having two external libraries (1 per user) running with writing access.

Since I am running a system with an HDD and SSD, I am a bit confused about the the several sub-folders that come along with the "Data Storage (aka Upload Location)". I would like to make full use of the SSD performance.

What is precisely stored in the folders library, upload, thumbs, profile, encoded-video, and backups? Which of these would profit from being switched towards the SSD. Which of these would cause the high SSD/HDD wear down as described in this video (https://www.youtube.com/watch?v=TqjlUocu6ZI)?

(I plan to not really use the immich upload function and just have a syncthing-synced folder in my external library if that matters.)