Nope, leave smaa on, you need some antialiasing even at 4k and smaa is low impact post process AA and has virtually no performance hit.
Since I have the same spec as the OP, I can say with certainty that he should be getting way better FPS than he's currently seeing, 100fps+ everywhere @4k/ultra.
I'd try the following:
-Make sure you don't have supersampling set above 1.0
-Update your driver's
-Re-seat the GPU and disconnect/reconnect all the power cables.
+Try the same dogfight in solo play, no matter how powerful your pc, you only need one fool playing on a dialup junk connection to drag an entire instance of cmdrs into slideshow territory.
Beyond that, I'd check the performance of the card itself, run something like unigine valley or 3d mark firestrike and see if your results are similar to others. Same goes for CPU performance, download cinebench and make sure you're performing as you should be. For reference, my own 8700k hits a score of 1652 in cinebench, and my GPU gets around 6637 in unigine valley benchmark (extremeHD preset), you should see similar scores, if you don't, it may be a faulty CPU/GPU.