This has already been covered well, but wanted to add in a little. NVMe is not a cure all for speed. When working with large files where you have a write op that takes many seconds, NVMe CLEARLY has an advantage. If you’re working with smaller files, you may find that buying higher quality SATA SSDs work better. This may sound counter-intuitive because of the interface speed being limited to roughly 750 MB/s (6Gbps/8), but the facts are that working with small files slows down ALL drives of any type, and the advantage a SATA SSD has over a PCIe NVMe is form factor. For instance, Samsung can get V-NAND 2-bit MLC inside the SATA SSD formfactor at a somewhat reasonable cost, considering the speed it gives you with random read/write ops with smaller files. It’s basically impossible for Samsung to put memory that fast on an NVMe, with any capacity larger than 256GB, and the costs are in favor of the SATA SSD.
An example: SAMSUNG 860 Pro Series 2.5" 1TB SATA III V-NAND 2-bit MLC Internal Solid State Drive (SSD) MZ-76P1T0BW.
The bottom line is, if you really need top speeds, you have to understand your usage, which type of memory storage chips are better suited for that usage, and what is your capacity requirements. If you only need this to be a swap area for creating files, which you will then move to another drive, then buying 4 256 if perfect, but you still have to consider the quality of the NVMe’s and the type of memory they’re using. I consider building files to be similar to writing small files, as whatever application can only write parts of that file when that specific part becomes available. If indeed you are creating files with video editing or various other reasons, and you NEED the speed, AND you can deal with 1TB being enough of a temporary storage area for the files you create (I need about 4TB so NVMe RAID is too costly for the speed I need), then something like a SAMSUNG 970 PRO 512GB M.2 2280 PCIe Gen3. X4, NVMe 64L V-NAND 2-bit MLC Internal Solid State Drive would work well. I don’t know if you can find a 256GB variant of something that will perform to this quality. You probably could 2 - 3 years ago. Check out the specs of something like this vs. other NVMe’s, and you can’t look at the one “PRETTY” stat that shows off what the drives do with a sustained transfer of a LARGE file. If you are constantly building files, then you want to look at the random read/write results with small files.