Consent-o-matic is about consent forms, so it'll fill the consent forms giving, by default, the least consent possible. If it doesn't know how to handle a form it'll just not auto-fill it so you'll have to do it yourself. It's not just about cookies, they are just one common way to acquire the data. IDCAC will just hide the form, because it was made to hide cookie notices and later extended to do the same for consent forms. According to the law not filling the form, not giving explicit consent, is like refusing it.

Anyway, none of these extension touch cookies directly, they are only about notice and consent forms. It's up to the website to act accordingly. And none of this will do anything about necessary cookies, or more precisely, about any data deemed necessary, however it's collected.