I only need two more to answer all your questions !
At the native res that's 14,860,800 pixels to push. Almost like 8K with many more 3D objects in view. SLI or not and Gsync notwithstanding, the GPU capable of handling this in games does not exist yet...
But I'd be more concerned about "edge distortion" - the portion of the side screens showing increasingly stretched graphics in games with a single camera frustum (ie 99.9% of them). YT videos of TripleUltraWide setups are very good at not really showing you this. 3x curved 21:9 is very attractive on paper but I'm afraid there is a point where wider becomes too wide. I too can't help but wonder, though