You can change everything in a crossover but the point is what do you want to achieve. More detail, different character?
The easiest part are the resistors and internal wiring and most likely what you refer as a sweet spot. Capacitors are costly, can bring a very good improvement but can also expose drive units. With wrong inductors it can get a real mess.
I agree with all posts above, leave them in factory form unless you have good experience in parts and building crossovers as not upsetting speakers' voicing.