If you go the butyrate route, its like Tommy says, don't try to use it with anything else and, then, you don't need to clear coat. The butyrate colors come out the same as the clear. Don't forget about the blushing with high humidity and pulling loose in the corners if you get it too wet problems. Used it for years, glad I don't anymore.

The three water based polyurethanes I've tried all etch or turn into a gooey mess if fuel or exhaust residue hit them for any length of time. Others report success with some very specific products, but be sure you get the exact label name as there are similar sounding ones that don't work. The oil based poly's do yellow, the water based ones don't.

Of the choices you listed, I'd go with Nelson.