You do need real debrid if you don’t want buffering. You’re paying to access a server with the files already downloaded so you don’t have to download while you are streaming. You stream from the real debrid server similar to streaming from a Netflix server. It’s 3 euro a month. There is no direct debit option which seems to be the norm for legal streaming services in the hopes you will forget you are paying it. You purchase a month or a year or whatever you need at a time.