Affiliate tracking in ONTRAPORT is done through a cookie value stored on the contact's computer. The form processor code and our tracking script will read the cookie, and because they are active scripts, they should not be affected by server side cache.
Cache can affect protected pages in a PilotPress powered membership site on WordPress ... the protected pages are served from cache rather than the database, so PilotPress cannot prevent them from being displayed. But if you are not using protected pages in a membership site for your landing page then you should be fine with caching. At least in terms of the affiliate tracking!