I don't really get what people are saying when they say that Toei didn't try with the filler for Whitebeard and Roger, but I'd argue, they definitely do go incredibly hard. I wouldn't say it was underwhelming in the least.
This episode had a lot of incredible animation and animators on it. I'll go through the opening fight scene by scene, but first I'd like to say that even outside of the action scenes, there was a lot of nice character acting animation in the first half of the episode that added a level of expressiveness to the character's emoting. Stuff like Roger point at Oden, that nice bit of eye animation where Oden makes up his mind, or when he lurches forward in surprise, and Whitebeard creating quakes were all really nicely animated things that gave that scene a level of movement that enhanced the character drama. Certainly not the most noteworthy part of the episode, but still nice to see some level of animation consistency outside of fight scenes.
The opening brawl between the Whitebeard and Roger pirates was animated by Masami Mori. It was a really solid scene from him, even if it wasn't as lengthy as his work on 957. Lots of cool stuff here.
Takeshi Maenami, another phenonemal animator handled the later parts of the Whitebeard v Roger clash. Lots of cool impact frames and poses that I enjoy, even if the action isn't extensive and more effects based.
The opening clash of the episode was animated by Tu Yong Ce, who was also an animation supervisor during this scene. His scene has a lot of great acting. His character art is as strong as also. The last 10 seconds of the clip is animated by Junwen Tan, whose pretty much become Tu's accomplice effects animator at this rate.
Tu also animated another short bit of action with the Whitebeard v Roger pirates.
I think something really exciting, is that a fan of the series actually made his animation debut on the show this episode. He didn't animate a particularly action heavy scene, but his work this episode was still stand out nonetheless. He has really interesting line art and effects. Hope to see more from him in the future. I really enjoyed the cut of Oden emerging from the smoke.
(I'd post his twitter confirmation, but Worstgen has a limit on the number of media links allowable).
Overall, aside from the action, I thought the episode was really solid. I did prefer the first half to the second, but the second half was still pretty fun, with Oden's shenangins making him a very endearing character in the anime. I really enjoyed his little dance about making oden.