Merit, at most every school, doesn’t require any financial aid submissions.
But to answer your question, being wealthy and showing so through submitting a CSS, shouldn’t impact any merit you’d receive.
Of course, most schools are opaque other than to say they have merit. Some public schools have merit tables so you know what you are getting.
If you have the time and ability to submit FAFSA and CSS, I would and did.
And I can’t imagine merit was impacted. After all, it’s merit and not need aid.
And the schools themselves will tell you it isn’t. It won’t even be the same group of people evaluating one vs. the other.
Good luck.