The SpongeBob SquarePants Movie: ENCORE (or just Movie Encore) is a mod built off of Movie DX. The mod itself aims to be a New Game+. As such, not a lot is changed from Movie DX. However, there are still some changes.
In typical Koopa Eliminator fashion, most levels have different cosmetics, but there are also harder enemies, some more/different enemies in places that never had them, mirrored and sped up Floating Block Challenges (except the final one, which is simply mirrored), faster boss battles, some faster & harder obstacles, reverted and a couple moved rings for the Ring Challenges, and the biggest change... no SpongeBall Challenges They have been replaced with a "new" kind of challenge, the Star Slides!
This google drive folder contains a download for the mod, and a Steamgrid folder in case you wish to add the mod to your Steam Library.
It also contains two text files that are highly recommended to be read.
Disclaimer: It is highly recommended that you create a backup of your TSSM iso. Just in case something in the mod installation process goes wrong.
Check this video out if you want to build the mod as a rom https://www.youtube.com/watch?v=uK5HI6fQVK4
Alternatively, you can use this article here, if instructions through text is your cup of tea. Setting up Dolphin for Modding