Has anyone used Ron's fogs and smoke? Is it possible to use it in Daz or Bryce, or just Photoshop? If not is there any way to get that in Daz?
You can create images with them that you can use in DAZ or Bryce, but they are really just photoshop brushes (which can also be used in Gimp with a little effort).
Is there a way to add that type of 3D fog that would be, or have the characteristics of an obj file?
You could use the brushes to make diffuse and transparency maps that you could apply to a planar primitive.
If you want ready made 3d fog there is Age Of Armours camera shaders...which do a fog effect or jepes has a fog prop in daz's store.
There are some fog freebies at sharecg.
download this to see how its done and just modify to your liking
RDNA also has freebie weather effects; even if they are intended for Poser, I found out that they work just fine in DAZ too.