There is a different API site for each version of Solidworks (year). I believe you can just change that value in the URL to get what you want.
Usually when I want to get the interface page, I'll search google like this:
i[ObjectName] Interface Solidworks api [year]
The "i" before the object name seems to help. I have no idea what the distinction between iModelDoc2 and ModelDoc2 is but the former seems to be easier to search for.
It doesn't always work out. Sometimes the top results will be example code; but it gives the best results in my experience.
One solution to this problem would be for the SolidWorks team to link to the objects used in the API examples since they seem to dominate the search results. You can usually find examples from the Interface page but it is often difficult to navigate to the interface page from an example.
Note that the API documentation for certain functions is rather minimal, sometimes inconsistent, and not entirely correct. If you are troubleshooting a bug or unexpected behavior, don't take the documentation at its word.
One example of inconsistency regards methods for getting points. Some methods return a MathPoint whereas others will return an array of Doubles.
An example of incorrect documentation: CustomPropertyManager Set return values Although this could be a mistake on my end; I haven't recieved any feedback there.
The API help is also available locally through SW through the help menu.