Yes, manga can have fillers. Sometimes authors use them to flesh out characters or settings, or to give themselves more time to plan the main plot. But too many fillers can make the story drag.
The Naruto manga itself doesn't have fillers. Fillers are a common thing in anime to extend the runtime or bridge gaps in the manga's story. But the manga sticks strictly to the main plot.
In general, the Bleach manga is free of fillers. The plot progresses smoothly without any detours or extra content that's not part of the original narrative.