He probably means the 8 frames of lag SFV has, and if he can’t feel the game is horribly laggy compared to other fighters then I don’t think he will really notice a difference between a sub frame monitor and one with 1-2 frames. Either way the good Asus and BenQ monitors input lag are around the same.
Little bigger than what you’re looking for, but both Acer and Asus make a 34" ultrawide /w g-sync (I believe Acer has a freesync model as well), both have low input lag and fast response times. $$$ though. Why UW tho? SFV won’t do 21:9, even if you set to a 21:9 res it still renders 16:9.