No, do not edit the ACF files.
You need to add the code you your functions.php file.
I’m going to be honest though. After giving this some thought I’m not sure it will work 100%. I don’t know what plugin you’re using for templates but its safe to say that it doesn’t use a standard wp field of any kind. This means that the field groups will not change automatically when you change templates. You would need to change the template and save the category to have them change.
