Well I'm not a lawyer so I certainly hope no one is considering it legal advice. But CBP has pretty broad authority to detain you at a point of entry. They can't deny you entry if youre a citizen but they can detain your ass for yours and confiscate your devices.

As a non-lawyer, things will go much more smoothly if you just answer the questions and give them your devices. If you've done nothing wrong, there's no crime to charge you with. If they want to fabricate charges, they'll do that regardless of what you say.