HDD drives in new NAS - compatble?

[Enquiries]

I am moving my media server to a proper NAS for home use (music/video streaming).

I currently have a 4TB WD Blue drive. I'm thinking of buying a new 4TB WD Red drive, which is more equipped for NAS use.

The two drives differ in RPM and transfer rate. I've not yet decided if I'll utilize RAID to mirror the two; if I do choose to do this, will the different RPM and transfer rate make the mirroring unstable or would I be better off using the two drives as separate storage?

[ed]

You can use them, just keep in mind that performance will be affected based on a slower drive.
When you use the m in a NAS you will need to format them. You can either mirror them or have single volumes.