I'd keep the localized cloud, just for the sake of render speed.
If you mask by distance shader or sss TG still needs to test the entire planet's cloud layer to see where the distance shader/sss applies --> slower.
To make it easier to work with them just set up a new separate camera which looks down upon your scene.
Then let the preview render finish and point your mouse in the 3D preview where you want your localized cloud to be.
Right click your mouse and select "copy coordinates" and paste those into your cloud's localization position parameters.
That's it, ubersimple.
I like the spray as it is. If I may I'd suggest to add warp to the density fractal.
Easiest starting point is to use the warp function from the fractal itself (last tab).
The scale that warp function works with is the lead-in scale.
Say, if the spray is 2m tall then set the lead-in scale of the fractal to 1-2m. Then play with warp strength.
Changing lead-in scale may change coverage of your fractal, so you may need a re-seed.
Ultimately you could duplicate the fractal and have each warp at a different scale/strength, then merge and then use that as density function for your cloud.
Of course you can also warp using the warp shading in conjunction with a redirect shader to control which direction the warp is going.
Endless possibilities
Cheers,
Martin
