Answer
Use save advice carefully: demo save behavior and full-game save behavior may not be identical, so check current in-game prompts first.
Treat Piggy: Intercity saves as route-important because choices can be permanent and can affect relationships or outcomes.
Before making a major NPC choice, assume it may matter later. If you want a clean route, slow down, read the related quest or character page, and avoid attacking neutral NPCs casually.
If you need to reset major choices, treat starting a new save as the safer assumption rather than expecting every decision to be freely reversible.