I'm really glad I found this mod, I've been wanting something like this for a long time!
One suggestion I have is that you add an option to make the smog more focused around the edge of the screen with a slightly clearer area in the center. so you can see a region around the player a bit easier while still getting the feeling of being enveloped by the smog. And maybe options for how large the smog-border should be, how much clearer it is in the center, etc.

Idk how difficult that would be to add, but I thought I'd throw it out there anyway! <3

It already works like this, so maybe you want to tweak some related settings. The Opacity setting controls how not-see-through the smog is, and the See-Through Opacity is a separate control for two "important" areas: your camera's position and the position of the entity that your cursor is on. So, you can lower the See-Through Opacity to make it clearer.

It cannot be as you described, with a perfect center-to-edge transition, but it's basically the same as you're describing.

Ah ok, didn't realize that lol. Thank you!