To me there's a discernible difference, so I decided to roll back to 12.6. It's a free world.
Tried that, and I screamed "OMG why does it lag so much?" ;)
Are you sure you didn't mistakenly change iShadowMapResolutionSecondary or iShadowMapResolutionPrimary? I did the first time and...
I have reverted to 12.6, I don't want to play with downgraded shadows. I hope they fix this for the official 12.7 release, since there should be big performance gains on Skyrim with 12.7, at least according to AMD.