Just thought i would add my experience with stutters as it may help others.
Had tons of problems with stutters on p3d and xplane 10/11.
My rig is quite old now (4 yrs) i7 4770k @4.7 water cooled..Gigabyte Z87 DH3P..Nvidea GTX 780..
Stutters disappeared in xplane 10 and now xplane 11 by reverting back to Nvidea 377.88 driver as advised on avsim forums.
Tried p3d a few years ago and had tons of stutters once I installed ORBX..gave up and have been flying xplane ever since.
A few weeks ago I downloaded p3d v 3.4 to give it another go. Its all working perfectly now on my old rig with ORBX base, vector, europe and UK....PMDG 777 and Rex soft clouds...p3d cfg NO alterations...NO Nvidea inspector...I followed this video by Matt (chewy94) and Medium settings.
Mostly with the PMDG777 I get 40-50fps...frames do drop flying in and out of Heathrow EGLL to around 26-35fps but there are no stutters at all very fluid.
p3d v 3.4 appears good on the memory issue too..mostly I land with about 1.4Gb to spare..never gone below 800Mb and that's on a 11 hour flight from UK to Hong Kong..