I think you have a fundamental misunderstanding of what you are trying to achieve. And are over complicating things which is confusing everyone.
It would help greatly if you could give some indication of what containers you actually want to use.
From the sounds of it you want a file server which is your nas. Then you want to run an application in a docker container on your Linux machine.
Using Plex as an example, you would mount your Plex directories on your Linux server via NFS, then start the Plex container pointing at the mounted directory on the Linux server.
Nothing would run on your nas apart from the nfs file server.
The image you linked looks a bit more like a distributed worker. I use something similar where one server runs the core services and then I run specific workers on multiple other machines to distribute and increase the processing power. I don’t believe this is what you want to do as if it was, you would probably know it.