primeval_god

It is but it is not recommended. Containers run through the console will not be particularly controllable via the webui.
 
There is a plugin which installs compose and allows for managing basic compose stacks via the webui. Like dockerman however its designed to support compose stacks run through its ui interface not via the console or other methods. Compose stacks launched via means other then the composeman interface will not integrate with the interface. 
 
If your goal is just learning docker or learning to manage docker systems in general i would not recommend unRAID as the way to do it. unRAID is not a general docker host. unRAID focuses on docker containers as convenient way to have "apps" rather than being a general host for the myriad of other ways containerization can be used (microservices, clusters, C/I setups, etc). Many of the best practices of docker on unRAID are not the more general docker way of doing  things (bind mounts preferred over container volumes for instance or running everything as root). If learning about docker is your goal i recommend using a VM or LXC container with a more general linux OS to host your container playground. Leave unRAID the unRAID docker host for running your important NAS services (media servers, backup servers, sync etc.).

This. Multi-user management is simply not a feature of unRAID (either officially or through community plugins). Generally i try and dissuade people from considering unRAID for business purposes as its security, update cadence, support options, and overall design goals are focused on home use cases. More specifically for your case i would not be comfortable basing business infrastructure on some custom workaround for an unsupported feature (multi user). 
 
If the above doesnt convince you my suggestion would be not to run your multi-user VM/containers directly on unRAID. Nest them within a VM with an OS that provides the multiuser control you need.  

unRAID requires a 64bit processor. https://docs.unraid.net/unraid-os/getting-started/

No, the Dockerman system has its own method of storing the current and latest available version of docker images. Compose.Manager does not integrate with Dockerman in this respect (in fact it does no update tracking of its own it just provides a button with runs a stack update command). 
 
No, at the moment there is no good way to remove the "Update Available" link.
 
The pings are from the Fix Common Problems plugin correct? Best to just disable the update check in FCP.

It is an unRAID concept. There is little more to it than placing all of the docker engine's internal stuff into a disk image to make it easier to manage in a system without the normal persistent install locations.

The guide is not directly applicable to unRAID. unRAID (thankfully) does not use systemd, and changes to its system files are not persistent across reboots. You would have to write a script to make the changes required to put docker in a cgroup (whatever those are) and run it on start before docker starts.

Not a bug but rather misleading documentation. Isolation is for VMs. Pinning if for dockers. 

There is not. unRAID users are not users in the linux sense. unRAID only really supports user access control at the share level through SMB.

I dont know for sure but i would suspect it is the file integrity plugin. The "Changed" time reported by stat is the last time that file metadata was changed (most docs list permissions as an example of metadata). The file integrity plugin stores its hash value in the extended attributes. What i dont know is if extended attributes are considred metadata in this instance, but i would suspect so.