https://wccftech.com/super-mario-3d-all-stars-comparison/

All games included in Super Mario 3D All-Stars will see improvements over the original releases, and Super Mario 64 is going to feature improved textures, as highlighted by a new comparison video.

Following the collection's announcement, GameXplain released a new video comparing the Super Mario 64 Switch remaster with the original Nintendo 64 release. While character models haven't seen much of an improvement, textures definitely have, although the improvements are not on the level most fans expected to see.