Have any of you used this specific product before? If so, I’ve got some questions
I don’t have any experience with #20, I use #77 quite frequently. I seem to recall that 20 is used for upholstery, particularly automotive applications. I think it comes out in a stringy kind of pattern, not a spray. This makes it easier to use in tight areas, where a fine spray will drift around.
If all else fails, test patches.
Good luck
-Wolf
“Comes with a lace spray pattern for improved accuracy” could be a euphemism for “comes out kinda gloppy” 
Yup. That was what we were trying to sort out. A sample has been tried, and it seems ok ish. Spray adhesives are wonderful, but so weird sometimes