Im almost done with my own rewatch of the series and the only filler arcs I watched were "anime canon", those being the Bount arc and the Gotei 13 Invasion arc. Basically, it means the filler arc is integrated into the story and potentially shown in flashbacks during otherwise canon scenes. Annoying, but I powered through. Those two arcs aren't particularly terrible, but they aren't great either. The other filler arcs, like the New Captain Shusuke Amagai arc or the Zanpakuto Rebellion arc occur at random points in the series and can be skipped and rewatched at any time. When the series was airing I always hated when they did that. One second Ichigo is in Hueco Mundo fighting for his life, the next he's back in the human world acting like nothing happened. At least with the Bount and Gotei 13 Invasion arcs if you were an anime only watcher you'd have no idea it was filler since they're treated as part of the main story and even referenced in canon scenes.