You should never use Plexus on your paint protection films. Venture themselves when I spoke to them said do not use it as it tends to yellow the film quicker.
Plexus is meant to be used on true plastics such as Plexiglass, your instrument cluster, your nav screen, your headlights (if not covered in venture), tail lights, etc. You get the idea.
The best way I have found over the years on how to maintain the Venture film is to get the finest grade clay, and use that every 6 months on the clear bra. Don't clay your film as often as you clay the car. When you do clay it, apply minimal to no pressure, just glide it gently up and down the surface. Do the vertical panels in a up and down motion, and do the horizontal panels in a top to bottom motion, not side to side.
You CAN buff the PPF with a very fine polish such as Menzerna 106ff or powerfinish with a finishing pad.
You can also put a sealant over it as I have been with no issues. I use Menzerna powerlock on my film. However, I never put a carnuba on the film like the rest of the car.
Don't ever use alchohol on the film or any sort of solvent. No simple green or anything of that type.
Good luck man, let me know if I can help you with anything else.
Would you like pictures of my AW 335i with the Venture on it after 1 year? I can provide you two different AW 335i's that I had with Venture on both with pictures from 1 year later showing that the film never yellowed or discolored.
Let me know!