Sorry about being vague. What I meant was that one bottleneck for some people has been large projects with a lot of VST instruments playing back in realtime, i.e. not having been ‘frozen’ to audio tracks.
When I do SFX work I always try to transfer them to the local folder to keep that project self-contained. So ‘yes’, in my case SFX / library music lives on a “library” drive and get transferred to my local ‘work drive’ in the project’s folder. I’m guessing I could save some time loading from an SSD, but it doesn’t seem it’d be a significant save for me.
Those working with samples however might benefit from SSDs. I honestly don’t know, but I’m guessing it’s likely.
In my case all future drives will be SSD for work and spinners for backups and libraries. I hate spinners so fewer is better.