Salt is salt unless you are using some sort of flavored salt. Kosher salt, sea salt, and table salt, as well as most other types of salt, are primarily sodium chloride (NaCl.) The reason you see different amounts used when using different types of salt is because of the coarse nature of some salts or the crystal density. If you measure salt by weight rather than by volume, you would use the same weight in any recipe.
That being said, there is no salt that is 'saltier' than another salt when you are using the same weight measurement. When you are mixing a salt with other ingredients for a rub, I would not hesitate to say that your palate won't be able to detect any difference from one type of salt to another.
Kamado Joe Jr. ° Kamado Joe Big Joe ° Kamado Joe Classic ° Old Country BBQ Pits Brazos Offset
UDS ° Traeger Lil' Texas Elite