People will tell you different things about the theory: hwnna is nearer or in sight whereas hwnnw is further away or out of sight etc.
In practice however, not many people make distinctions like that. For all intents and purposes, hwnna and honna are the everyday spoken ones, whereas hwnnw and honno are more formal.
When it comes to hynna and hynny though, both are used, the former more in the north and the latter in the south. They're often shortened in speech to 'na and 'ny.