Hey Brady - I have an account so can give you a brief run down.
Models/Performer can set a monthly sub fee lets say $9.99 which allows you access to their newstream, think of it like facebook main and also enables you to chat on inbox to them, buy any extra items within the feed (if they wish to sell) i.e might be a video which has a $10 OPEN fee.
"SPECIALS" are often just discounted for an "X" time period, some might be 1 DAY FREE (although it may charge you standard $9.99 following that if u dont cancel it upon joining) or 40% discount for 1-3 months etc... Depends on the person running the account what they offer.
Onlyfans take 15-20% of all models earnings, so a good way to get a better price is contacting them directly and pay them on other payment methods, which gets them the same money & also you a cheaper rate - if your buying videos or what not... Many models will opt for them as its less of a trace record for taxation purposes (trust me - in about 2-5 years, thousands of people are gonna get screwed from not paying tax on earnings on onlyfans, lol).
Often people think this is ridicilous and partly why mine is FREE still as i'm unsure what I want to do regarding it all.
If you want to follow someone like my account which is FREE without it being a SPECIAL FREE: you'll always need to have a bank account/credit payment linked to your account: this is mainly to get an identify confirm off you, payments can be set to anonymous on your bank statement.
Hopefully this helps.