I found this by accident, but I thought it was pretty neat. It's the Tunnelers' Dream Preset, but the amount of bedrock is changed to 120 instead of the usual 230 because of building height limit. You could think of it as fog, but I like to think of it as heavy clouds. If you're standing on the ground, the clouds will not affect you as they start 2 bricks off of the ground and are 5 bricks high. They do go through walls so I'd suggest making your buildings raised or floating, because it does get slightly annoying.