After ensuring all of my settings were correct (my HDR got turned off in Windows, not MSFS, and my power settings reverted to “balanced” and not maximum performance) as well as these settings, I am now at 25-30fps on 4k HDR. I would encourage you to take a look at these, even if you think you’ve already done them.
I def see a performance hit from the latest update, but it’s far from unplayable for me.