السلام عليكم When do I count as a musafir (traveller)? I heard 3 opinions: first after 83km, second after 129km and third if you only leave your hometown. Could you please clarify which of these opinions I should follow, and how I should practically apply it?

None. You are considered a traveller if your journey is normally considered as travelling by your societ/community. So whoever makes this trip normally packs their bags says their goodbyes etc, then we consider this to be travelling this is the view of sh al islam and imam ibn uthaymeen