OptionsSwap changes the settings file used in standardoptions.txt for all of your chosen instances at once.
The files aa.txt and rsg.txt in the data folder are just examples of what you might switch between, you should copy your own settings into rsg.txt. Add all other options files you want to switch between as well.
Edit mcpath.txt to have the path to your MultiMC folder.
The program will edit the standardoptions file in your chosen instances to just contain the path to the selected file in the data folder created by this program.
If you change multiple instances at once (for example, the wall) I recommend grouping them in multimc and then selecting that group rather than each instance individually.
This program will delete anything you have in your standardoptions.txt in the instance's config folder and replace it. Make sure whatever you want to save is saved in the data folder (you won't have to type it out again, so give them descriptive names if you have a lot)
Credits to mowcus for the idea to make this :d
dm on discord if you need help @shnenanigans