Are subnetted devices located together, or can they be spread out geographically? Alternatively, for a more

Subnetting = logical, not physical.

You *can* have devices in different racks, buildings, or even continents on the same subnet, but why would you?

Most folks subnet by location to keep things clean.

Example: AWS VPCs let you span subnets across AZs, but they’re still logically separated.