It shouldn’t really scale above a certain point, it’s just that if you import a lot of pictures all at once (in my case with immich-go, as mentioned from a Google photos takeout), all the ML-Tasks (facial recognition, search tagging) together with the normal tasks (thumbnail extraction, video transcoding) can suddenly increase the ram usage from in my case normally 1-2gb to around 6, which even on an 8gb raspi could get a little tight. But for example even just 16gb in the HP should be enough, assuming you don’t have a bunch of other stuff vlogging up your RAM. As for the CPU, I’m not Soo sure tbh, I’m using a Ryzen 5 5600G, which can handle everything that’s running on my server with ease. I think the only significant downside you’d have here going with 4th gen is power efficiency, I still have an i7 6850K (OCd to 4.3GHz) in my main PC, and that thing uses a couple hundred watts when fully loaded, compared to my Ryzens 65W or so.