Making use of multiple disks to improve performance

I'm just starting out using jellyfin and I'm wondering about running multiple streams. All my media is on one 14 TB 5400RPM HDD. How many video streams can that support? I also have a 1 TB NVME drive, and that is a lot more space than I need for the OS and programs. Can Jellyfin use any of that space as a buffer or cache or something to support faster streaming or more simultaneous video streams? I don't know the terminology. Thanks.