The correct name is "Optional Sideloader Modpack Studio" - now you can see that this is a modpack ONLY for StudioNEO.
U can´t use it ingame.
The other one is the so called "Better Repack", current version R15 - it´s the game + tons of common mods for the game + a base version of StudioNEO.
For playing the game and creating your own character cards you need this Better Repack - 68.2GB to download.
Main site for the BetterRepack is here
You must be registered to see the links
How to best handle this read here
https://f95zone.to/threads/honey-select-2-libido-dx-r7-illusion.53457/post-8964484