I have never downloaded png3.2 so I don't know if install options are exactly the same as my 3.1+3.2updater : there is an install option to not check gtr2 files, this is the best option with modded install.
There is also "slim down" option to delete all gtr2 modern content but my setup can do the same.
By the way, hq cars use hq tracks and not base tracks which are unmodified like base cars, so there is no problem. Moreover, my setup allows to restore original gtr2 files, or original png files, or hq files anytime with hundreds of combos (I have never counted but the possibilities are huge).
Since I made the GTR2_SETUP, order has very little importance whether you install hq patch before png or after, in the end the most important is the setup to patch png install.