I found that moderate compression (like zstd-2 or -3) not only increases your effective storage capacity, but increases R/W speeds for HDDs.

At the time I got my current system, I did 1tb SSD for the main, and a 4tb HDD for data drive.

For my next system, I think I'll split that a bit more evenly, as most of my games end up on the HDD which means they a bit to load