I was just wondering if anyone has any tips or advice on wearing a binder but making it seem like my chest is flatter? Even with my binder I often feel like people can tell what's underneath. I know that it's probably just my head realizing what's underneath which was already pointed out and told to me by many friends. But it still bothers me and I just want to find a way around that paranoid feeling if anyone knows or has any suggestions that would be great! I highly doubt there is very much I can do but if I can't do much is it dangerous to get a binder that is this a smaller size than what I'm supposed to be wearing?

Don't get a size smaller - you'd be at risk of massively damaging your ribs.

Most people advise wearing baggier shirts, layers with shirts and wearing textured / patterned items (distracts from any existing texture or 'lumps').

Yea, a lot of people wear binders with baggier clothing. Hoodies and so on. Darker colors too. Some people hunch their shoulders. I used to, I wouldn't recommend it, not good for your posture in the long run.

A smaller binder as well as damaging your ribs will tend to make your chest look bigger, because of how tight it is. Dark colours work as well as layering. As long as you are confident less people notice than you think. Lots of cis men have noticeable chests; whether because they're chubby or because they're muscular.
I remember being called up to the register to collect my prescription and I was still called young man before I gave my name. Despite wearing my old binder that doesn't bind at all and my hair being a mess (I was in a rush to get my prescription).