Wow, was I disappointed at first but I seem to have ironed out the flickering issue for my system.
This is how I went about it.
I set everything in P3D and FI at minimum including disabling FI SMAA.
First up is I want to run at maximum FI resolution and get the best gauges possible so I set FI to 3840x2133.
I found that with everything at min or disabled, I could run 3840x2133 with no issues.
If this is all I could do I would be almost happy because 3840x2133 looks so good.
This is the point where I thought I'd try to just get the best cockpit possible so I started increasing FI SMAA and P3D MSAA as well as P3D texture filtering.
Here I discovered that I quickly ran out of headroom and got the flickers if I did much with P3D MSAA. After a lot of back and forth I found I have to leave that set to NONE as well as FI SMAA set to DISABLED.
P3D Texture Filtering did not seem to have as big an impact but I did find that as I increased other settings I had to keep notching it back. I'm currently at 4X with no flickers.
During all of this I tried all my setting changes with all levels of Tessellation factor and found that none of the settings made any difference whatsoever. It is as if it's a broken control. After everything was done I set it on ULTRA and forgot about it but it didn't do anything anyway.
Now that the plane was looking awesome my next priority on the wish list was to get the land textures back as much as possible. I ended up at 1m on Texture resolution.
For me the world can do without those goofy looking boxy buildings but I need me some trees! After all was done I ended up on NORMAL for Autogen vegetation density.
With a crisp plane, trees and farm fields below, I was about as happy as I could be. But I was missing airport structures...
These came back by setting P3D Scenery Complexity to Normal. To my surprise the flickers did not come back and I was at ORBIX Juneau at the time and that's a lot of structures.
Here I discovered the water was horrible so I punched that up to Low with cloud reflections to bring back a decent surface. So far so good.
Lastly I was able to bring back some cockpit shadows for the cherry on the cake with a setting of Low with Internal vehicle cast and receive.
It seems to me that the killer was always P3D MSAA. I just can't seem to ever touch that thing so it is left to NONE.
MAX resolution on FI at 3840x2133 is AWESOME! love my gauges. I wish I could go another setting higher because I think I could get more but I ran out of buttons! Next version maybe?
I ended up going down in frame rate to the 60s at times with a bit of the candy but the flickers didn't return. The following screenshot isn't totally representative because it was during my water tests but it does look good.
EDIT:
A2A Spit at ORBX Rohnerville doing well also...