Hi @June24 you already have it correctly set for a maximum of two guests per room, there is nothing that you need to change. Are you actually getting inquiries for 3 guests, or are you getting inquiries for two guests and they are asking you about adding a third guest?
BTW, if I'm a guest and making an inquiry on one of your three rooms, I wouldn't necessarily know that you had two other rooms - there is no "hosts other rooms" button when searching. You do mention in one of your listings that they can book another of your rooms but you can actually indicate the link to your other listings in each description. While external URLS are redacted, Airbnb URLS are allowed by the system.
Good luck!