Best practices for signing a plugin

I'm currently preparing my first plugins for publishing them. 

I have some questions related to best practices for singing them

I'm using Maven for the build process. Is it possible to access an keystore outsde of the current project folder eg. by using an relative path like ../../mykeystore ? In this case I would have a single keystore for signing all plugins and the keystore would be outside of the public repository (teh plugins are stored on GitHub).

Do I really need to generate a new key or is the better approach to use a known key for it (eg the key linked to my GitHub profile)?

TIA + Best regards,