256 is not enough for a serious main drive in a DAW. Sample libraries should all be on the fastest drive. There are single instruments that take up 50GB. And consider that most studios are recording in 24 or 32 bits at higher frequencies than 44.1Khz. 1TB is probably enough for a music production system although I'd personally prefer larger so that I don't have to be swapping things around all the time.
Maybe you haven’t looked around in a while; the toasters are Thunderbolt-attached now, and they take (en-cartridged) NVMe SSDs. There’s nothing slow or high-latency about that. Copy your assets over to your project disk from your NAS at the start of a new project, and then forget about it.
Alternatively, forget hotswap and use a Thunderbolt DAS with RAID6. Burn your projects from your DAS to a portable SSD when you want to pass them over. Only takes a minute or two.
