By and large what @T26E4 says is correct, IMO. It is when you get up to the most competitive schools, that the stats really do start to blur together. A lot of kids with 34 ACTs, 4.0uw GPAs, class val, etc. How does the adcom differentiate between those kids? That’s when the ECs can make a difference–but obviously in that case they are looking for passion, depth, and high levels of achievement, not padding.
It can also make a difference at some LACs that are not the most elite, however. Because their freshman classes are relatively small (as compared to state flagship U) they might have gaps that need to be filled. For example, when we visited Earlham they had just completed a beautiful new art building. They are also trying to grow each class size by about 50 per year. Putting these two things together would there be a slot there for a B student with a demonstrated extracurricular involvement in art? I would think maybe so.