I've taken a closer look tonight and performance and quality. I refuse to go lower than High-End in settings, it just looks miles better than medium.
So at 4K I am GPU bound by my 980TI, I get around 20FPS over San Fran with dips in frame rate. It's playable, but, not great.
Switch to 1080p frame rate is a lot better, but now CPU bound by my 4470K. However, running non native res is not nice on the best of days, on a 32" 4K monitor, it just looks really horrible.
I'm in two minds what to do to improve performance here. I could either buy a second monitor, either 1080p or 1440p and run with that, or stick with 4K and spend a lot on a new build when the time is right for components. Damn this sim and damn 4K for spoiling me, not sure I could go back. But then you look at the highest end GPUs and they are scraping in to the 30FPS @ 4K, add some fancy 3rd party aircraft in to the mix, and we will be back in the 20FPS territory again. Gotta love flight sims.