Actually, you want to ballpark how much merit you need and understand it as a % of COA, 20K a yer merit at one school might still be more expensive than full pay at another. And this is stats driven, good but no cigar might mean nada at good merit schools, mediocre stats might get sweetener $$ at an expensive school that offers pandering $$. Some majors are just brutally competitive in merit generous schools, say CS or popular eng programs where the competition is already tip top because that how CS and eng rolls.
None of this is binary. That is why there are so many threads here.