Can anyone share their recommendation for which brand of ND filter to get for my new P4P Pro V2.0? (of course the filters for the P4P V1.0 would work so anyone with those please share your opinions. Thanks.

The polar pro cinema series work very well, they make both ND PL and ND.  I prefer the ND PL as PL can make a huge difference when working with water subject matter to cut glare.  Also helps a lot on tree/foliage depending on the angle of the sun.  Of course you also get the polarization of the sky, which can help.  

Tiffen also makes a series that includes just a PL filter, however they are heavier and might cause a gimbal recalibration.  

Paul Caldwell