You cannot create Droplets in certain datacenters due to limited capacity. If you have snapshots in a limited capacity datacenter, transfer them to another datacenter to create Droplets from them.
You cannot downsize a Droplet from a snapshot. Data is not always stored sequentially in memory, so reducing the size of a disk can result in data loss or corruption.
Snapshots of Droplets are a best estimate based on the disk usage. Snapshots of volumes operate at the block storage level, so the snapshot size may not match what the filesystem reports.