Perhaps an example based on how I use my own drives? I haven't created video content in years but it may still apply.
I have three drives. a 1TB SSD, 4TB WD Blue, and a 4TB WD Red. Simplified, the arrangement is pretty straightforward- the SSD gets things that need to be very fast. the Hard Disks get things that are very big. For example the HDD(s) is where I have my file hoard- installers, downloaded ISO files, Video files, movie files, music, generic unsorted downloads, etc. Stuff that I don't use constantly and which will not be affected by the lower speed of the HDD. They got onto those drives because I put them there or copied them there. (coincidentally, this is where I have some recordings that I intended to turn into videos but haven't bothered but also cannot bring myself to delete...)
Most software I have installed is installed onto my C: drive, the SSD. This way it can access it's software files quickly. My OS paging file is on my SSD, and while the only software I think I have with the settings you mention (eg. Scratch Disk) is Photoshop, I have that set up to only use C: as a scratch disk- again, for performance since the two Spinning disk drives are much slower in comparison.
There are two things to consider here:
This is not all my drives though. Even discounting drives I have "in active service" in other computers, I have two Hard Drives, new in box, completely unused except to verify they aren't Dead-on-arrival- a 4TB WD Red and a 4TB WD Blue. They are specifically replacements for when mine die, since mine are starting to get on in years and it's always a matter of time before they fail. First sign of trouble, I clone the problem drive to the new one, replace it in my PC, and I have everything as it was with minimal downtime and (ideally) less risk of data loss. You don't need to install every drive you have in a PC.