Your specific questions have already been answered elsewhere in this thread, but I just want to add my usual plea to not use Portainer.

I’ve spent a lot of time with Portainer, both in my homelab and at work, and in both environments I eventually replaced it with Dockge, which is far superior, both for experienced users and newbies.

Basically, the problem with Portainer is that it wants you to be in an exclusive relationship with it. For example, if you create containers from the command like like you described, Portainer only has very limited control over them. Dockge, on the other hand, is very comfortable switching back and forth between command line and UI. In Portainer when you do create your compose files from the UI, it then becomes very difficult to interact with them from the command line. Dockge doesn’t give a shit, and keeps all the files in an easy location you choose.

Dockge will also do what you described in 5) take a docker command and turn it into a compose file. And it gives you much better feedback when you screw up. All in all its just a better experience.