From the videos I've watched there is still insane amounts of affine transformation texture warping, is that because it's not enable or because 2x is not enough?
I guess they will need to also redo all level geometry to be more amenable to tesselation... I guess that's why many ps1 games had blocky looking levels.
Unless I'm mistaken, the PS1 just plain doesn't support perspective correction. All texture mapping is done in hardware using a very not-programmable GPU; there'd be no way to do perspective correction, decent frame rate or not, outside of software rendering the whole thing (which would be beyond intractable).
The common workaround for this was, as suggested, tessellation - smaller polygons are going to suffer less from affine textures. Of course that does up your poly count.