FastCap Stealth Speed Brace, Primed, 3-1/2 x 12

I am going to have a granite overhang on a knee wall. The total countertop is going to be 18". Aprox. 13" inch overhang. Will this work?

Would this be suitable for a 30” bar top made from 12’ 2x10’s?

what is the guaranty/warraty?? is there any protection if the counter cracks/breaks?

What size/type screws would I need to purchase to install these braces?