If you see a visible difference when having FTXGlobal installed, compared to default, the most likely setting that can affect performances should be Autogen.
It's not true that a landclass product doesn't affect frame rate because "it's just new textures". If those new textures have new autogen definitions (and they have) which results in more autogen objects generated compared to the default landclass for the same area, there WILL be a performance decrease, so you might want to turn down autogen settings, especially in the N.Y. area, which is particularly heavy on autogen.