I totally agree about an SSD and a decent amount of memory, but for Photoshop and any other applications that involve some heavy lifting, think about the processor and the number of cores too. I use Photoshop and Affinity among others; I have a 2015 iMac 4Ghz quad core i7 with 32GB RAM, a 2019 MBP 2.3GHz 8-core i9 with 32GB RAM, and I upgraded a 2012 Mini with a dual-core processor to an SSD and 16GB RAM for my daughter. Running the same focus-stacking job on all of these, it took 4 minutes for the iMac, 3 minutes for the MBP, and 11 minutes for the dual-core Mini. I also ran it on my wife's M1 MBA with 16GB RAM, and it comfortably beat the lot with 1 minute 20 seconds. Perhaps I'm wrong, but this makes me think up-to-date multi-core processors, coupled with at least 16GB RAM, may be the way to go if heavy processing is involved.