Does a higher wattage mean crispier food?

Roughly, yes — higher wattage units (1750–1800W) preheat faster and hit higher temperatures, which bonappetit.com and seriouseats.com both flagged as the mechanism behind Ninja's MaxCrisp results. But wattage alone isn't a verdict; basket geometry and airflow matter as much, which is why several reviewers preferred specific models even at similar wattages.