jourverse was able to help me out with my question in a comment on this video.
I’ll quote it here:
For CPU, you need to adjust the PatchLength in OceanFFTData.h. For GPU, you need to set the user parameters of PatchLength in the Niagara system and adjust the material M_PreviewOceanWater’s CascadeSizes according to your PatchLength.
I was not doing the last step (modifying the material).