We are using utag.loader.RC and utag.loader.SC calls to load and store cookies in .js extensions. The same js extension is re-used for multiple profiles.
Are cookies profile specific? Or are they handled since the request would come from different domains associated with different profiles?
If cookies are not profile specific by default, what is the best practice to follow?
Technically: Cookies are not profile specific, but they are domain specific. Since you are using the Tealium method of setting cookies, they get set 1st party. So in a sense they become profile specific since the cookies are set on the current domain (1st party).
Non-technically: it's not something you should have to worry about. You can't set 3rd party cookies that can be read by other domains. The RC and SC functions only read and set cookies on the current domain.