Best to read all the developer documentation and watch all the videos. You may find that inconvenient, it was also inconvenient making the videos, it took a lot of my time, but a lot of important information is covered in them. If you are serious about learning mojoPortal development it is worth the investment of your own time to watch them. I think it will save you time in the long run.
Really the best tutorial is to study the code of existing features.
In mojoPortal features are self contained and there is no cross talk or communication between them. How you wire things up inside a feature is entirely up to you, though as I said you could follow examples of existing features. Myself I don't usually try to make one usercontrol manipulate another except in a parent child where a usercontrol may load and configure other usercontrols inside it but I don't typically make sibling usercontrols talk to each other.
Usually if you need to show and hide or load different controls based on user interaction inside a modulecontrol then you should wrap that in an UpdatePanel so the postbacks don't affect other modules that may exist on the page, or you can link to supporting pages for additional functionality as we do in more complex features like blog and forums.
Module settings are covered here http://www.mojoportal.com/modulesettings-adeveloperconvenience.aspx and also in the videos 28-30
Take a look at the latest code for the ContactForm.ascx.cs, it is a simple feature but uses some module settings. In the LoadSettings method you will see how it uses a wrapper class to load all the settings into a more friendly object ContactFormConfiguration which exposes each setting as a property. The settings themselves come from a hashtable named Settings that is intrinsic to SiteModuleControl base class, so the ContactFormConfiguration is just a helper class that parses all the settings into properties.