Writing MFTs for MediaFoundation

I recently discovered that there are (at least) two different sets of code inside MF used to drive MFTs.  People creating general-purpose MFTs should be aware of this fact so that their MFTs can be tested under both.

My question is: Are there only 2?

I realize that anyone can write their own code to drive MFTs, but at a minimum, MFTs should be expected to work with the standard MS+MF implementations.  But this is difficult to do if you don't know where they all are.

I see that the IMFMediaEngineEx interface has InsertVideoEffect.  Does this use a third driver?  Please tell me IMFMediaEngineEx doesn't use the (flawed) code from IMFPMediaPlayer...