It is true. I install OMV 3.x multiple times per day most days. There are harmless errors that people worry too much about. Commercial NASes just hide the errors. Whenever you install a php or nginx update, nginx and/or php5-fpm need to be restarted. This generates communication errors until the service is restarted. This is almost impossible to avoid but harmless.
As for the plugins, that is my fault. I have left the plugin not compatible with OMV 3.0.13+ in the repo because quite a few users are still using OMV < 3.0.13. That is why I said it is stable with the ported plugins. The list is always changing hence the lack of a list. OMV 3 is still developing. I have been using it for months but my systems are setup and not changing much.
It is very easy to remove/uninstall plugins from the shell. Remember OMV is just a frontend for shell commands. I posted the remove command in the other thread - apt-get purge openmediavault-wol
I really think you just need to be more patient. Once a server is setup and working, very little needs to be changed and that is when it shines. If you are installing things all the time, stability is reduced. This happens on all server - Linux, Windows, etc.
The plugin only works with OMV. There is no way for it to work with docker. Sorry.