JBoss Portal is defaulting the window state to normal. So if you have 20 portlets they all be displaid by default.
How to define a layout strategy and "what is the correct or preferable approach to it) "could be a rephrase of the question.
A simple and first approach to it could be to define a default value to portlet window state and mode.
Another way to do address it would be to define an "initial region" and allow a portlet to dynamically change region. Is that possible with 2.6? (I couldn't find it in the documentation)