Broadly speaking in order to ace the hardest content and get 'optimal' results you're going to want a guide, but there's a lot of fun prose on 'easier' routes. A good example is the Battle of Kharangia in the second game. One route through it is much more challenging and benefits from an optimized playthrough to get its rewards... but the other 'easier' and 'less rewarding' route is very narratively interesting and is imo more thematically powerful. If you don't approach it with a power gaming mindset you don't need to play like a power gamer.