Drives fails so always be ready for that.
How many drives you buy depends on your goals. I wanted a small nas so I’m using raid1 and just have 2 drives.
If your nas has more drive bays and supports it you can start with 2 drives and simple add a drive as needed. You wouldn’t be using raid at that point as man nas have more flexible options. My Synology calls it SHR.
This assumes you need simple file storage and not running multiple VMs with databases.
Yes. I don’t read Lemmy to watch videos.