Is an M.2 SATA SSD fast enough for an operating system, or is NVMe worth it?

The advertised speed gap is real—SATA SSDs top out around 500–550 MB/s, while NVMe drives can reach several thousand MB/s—but most operating-system activity consists of smaller random accesses rather than huge sequential transfers. You should notice the difference mainly when copying very large files or doing heavy storage work, not in system responsiveness or gaming performance.

For normal desktop use, an M.2 SATA SSD will feel very similar to an NVMe drive. Booting, launching applications, gaming, and everyday tasks generally won't show a meaningful difference. NVMe mainly pulls ahead in benchmarks and workloads involving large sequential file transfers.

One terminology note: M.2 describes the physical form factor, while SATA and NVMe describe how the drive communicates with the system. M.2 SATA drives and M.2 NVMe drives use different keying and aren't always supported by the same slot, so check the motherboard manual. If your board supports that SATA drive, it is perfectly reasonable to use it for the OS.

You don't strictly need a separate physical drive for multiple operating systems; partitioning the 1TB NVMe can work too. But if keeping the OS isolated makes distro-hopping or reinstalling easier for you, using the spare SATA SSD is a sensible choice. I wouldn't buy another NVMe solely for the operating-system drive unless you have a particularly storage-heavy workload.