with respect
I apologise for using RNAV, RNP and ANP loosely.
But... and it is a very big but... PMDG is not RNAV equipped. It only pretends to be. It gives a pleasing rendition on a PC but the gulf between it and reality is.... well unreal.
Try this "Turing" test... turn the Boeing off and on again and guess what, it comes to life and sorts things out; do that to the PC and at best it boots up. At worst you get a blue screen. Which is real and which is illusion? The PMDG is all illusion.
However if you fly the profile I suggested you will achieve a pleasing result, especially if you arrive at FAP configured and stable. Why not aim for that? Load the approach of your choice and "hand fly it" but don't imagine there is a suite of interactive electronics behind the scenes doing a "super ILS" for you. There isn't.
No I don't fly anymore. Yes I do know the B737 tolerably well, my last job but one was with Boeing. Now I work part-time on sat nav and GBAS as it happens so my slapdash terminology is unforgiveable. Old age I fear.
Good Luck!