The Vault documentation indicates that there is a master key and that multiple keys are required to access the secrets, but does this mean that Vault is not suitable for personal projects if there is only one PC?
Vault will distribute multiple unseal keys but there's nothing to stop you from keeping all of the keys in one place for a personal project.
The one time I did it I set the keys to 3 and kept them in different physical locations along with online locations.
One thing you should know is, even though you can backup vault(consul, if you are using one as backend), you cannot restore to a new vault installation (if you loose the existing one). You can just restore to the original one.