Hello and thank you!

So, just check that you are in the last version of iCagenda (3.3.7) as i'm adding new features and options frequently.

About submission form, you have global options or individual options in menu, to hide or show fields
So, you can hide registration field!

About registration button, in each event edit (admin side) you have options for button in "options" tab of an event edition.

By default, the registration button is using iCagenda registration form, but you can set it to an external link, or an article.
Note that today, the external (or internal) link and article link, are not in relation with iCagenda registration form.
In the future, when all current developement will be done, i will work on a paypal plugin for iCagenda registration form, which will able this. This plugin will be commercial for a little fee, and included in Unlimited version (but the planned date for this plugin is not before end of 2014, if every developements in process are going as expected!)

Regards,
Cyril