It depends on what loan amount that you are looking for.

“a 760 will get you much more than 680”
Isn’t necessarily true. Another myth.

The best conforming loans ($417K or less) the pricing is the same as long as score is 680 or above.

The underwriting is an automated system. It may give more weight to a higher score, but with an approval, the rate will be the same for a 760 as 680.

On a loan amount above $417K, different lenders offer different pricing. I think that the best pricing on a jumbo loan is on a score above 760, but a different lender may offer siimilar pricing at a 720 score.

Scores can vary by 30-40 points monthly depending on credit card balances and usage.

Having no balance doesn’t always mean that you score will be higher than having a balance.