Topping a coating is a super complex and long topic lol. Basically, my personal suggestion having played a ton of different coating stuff is that if it's a quality coating, leave it be. Drying aids for coatings are great, or not. There's so many different chemical reasons to or not to top.
As for graphene, I'm undecided. I have one car with graphene and one car with Cquartz UK on it. No clue, both are great. Drove through a rain storm with it yesterday. car looks freshly washed. Time will tell I guess?
To be honest, I'm guessing the reason that Gloss Coat is accepting the topping so easily is because Gloss Coat was designed to be topped. It was formulated to accept Optimum Car Wax or Optiseal, dealers choice. But it also means that a lot of other products will play nice on top of it. That being said, anything used to top a coating generally will not last as long because no full bond was established.
At the end of the day, topping coatings really are dealers choice. You don't need to but some people like to. I can say that topping a coating with the right stuff can take a manufacturers rating of 2 years to 3 years. I had a car that I maintained to close to the 4 year mark with CQuartz UK with toppers and what not on top. After a wash and fall out removers, still had no bonded contaminants. No claying was needed. When I did the polishing off of whatever Cquartz UK was left, the white pad I used didn't pick up a lot of embedded dirt, meaning that the coating kept itself relatively clean for 4 years. That's the real benefit of a coating.