Wide-angles are EXACTLY the type of lens the mirrorless cameras should be able to do far better than the SLRs, because the lens design needn't be compromised by the question of leaving room for the mirror.
I expect an RF 35/1.4 would leave the EF in the dust.
I'd say the RF 50/1.2 has literally 10x the resolution of the EF, and that's not even a wide-angle. (10x area means about 3x linear. And the resolution charts show the RF 50 has the contrast at 30lp/mm that the EF does at 10lp/mm. Ergo it's safe to say it's something like 10x sharper.)
Retro focus lens designs are generally used for SLR focal lengths less than 35mm. However, mirrorless designs still have a mount flange, so for ultra wides, a retro fcosu design may still be required. Canon could easily have created an ef 50mm f1.2 L that matched the RF 50mm f1.2 L optics but chose not too. The Zeiss Otus 50mm f1.4 and Sigma Art 50mm F1.4 are good examples of other brands fullfilling that particular brief. The EF 50mm f1.2 L isn't a retrofocus design, it's just one that was compromised for the need to be small, compact, bright and relatively cheap to build (Canon was going through a strange design phase at the time). It's easily the weakest L prime in the EF range.
An EF 35mm f1.4 doesn't need to have a retro focus design. So the assumption that a newer RF 35mm f1.4 would be optically superior could only point to a newer and superior design that has little to do with mount (EF vs RF). I think there would be more optical gains for an ultra wide zoom or a 24mm f1.4 on the RF mount. However, I've never found the ef 24mm f1.4 or 35mm f1.4 lacking optically. Maybe in a 50+mp world results will be different. But for wide open lenses...bokeh and rendering is king and not absolute sharpness. Stop down a few stops and most of the EF lenses are sharper than most zooms.