What type of schools are you looking at?
In general, I would assume merit isn’t tied to need.
If it is, it’s not merit.
Schools have university funds (your regular merit) but then additional scholarships that might be endowed. I don’t think there is issue with filing a CSS if you want to. We didn’t qualify for anything but I still filed just in case. The time a CSS would impact is if someone had severe need and a school was need aware and wouldn’t want to provide a large grant. But that doesn’t sound like you. And if it was, you’d need to file anyway to afford that school.
I’d never know if American gave us just $15K because they saw me as someone who can afford that - but I highly doubt it - because with such a lower offer, they lost a potential customer.
Here’s an example of merit vs. needing aid or other requirements - UNH
They have regular university merit but then have the Hamel Scholarship which is endowed and required for a New Hampshire student.
Then they have this one - The David Ellsworth Davis New Hampshire Scholarship Fund recognizes a student whose families have resided in New Hampshire for at least three generations.
Then you have one like this - Angelica Rose Basso and Vincent Luti scholarship - which clearly has a need component: Undergraduate students who are studying a major in the College of Liberal Arts or the College of Life Sciences and Agriculture are eligible for this scholarship. Recipients are selected by Financial Aid.