POLITELY assert your rights on the streets. If an officer asks if they can search your trunk, tell them that you would rather they didn't.

"Do I have to" and it's variants are deferential without necessarily ceding your rights in a way that "oh, sure" does. They don't need any cause at all if you give permission, and if you give permission it's going to be hard or impossible to argue later that it was an unreasonable search.

The sad truth is that you need to assume that you're on camera whenever you interact with a police officer, act as if whatever you say will be either edited and shown to the jury or described to them out of context to justify whatever bad actions the officer takes.

100% be polite and even friendly, but 0% on "just let the officer do whatever and think you can fight it in court later."

Very simple, “I do not consent to any search,” but do not interfere with armed people. Once you have asserted your right, you should not try to impede them violating them. Too risky. Let the courts protect you. Or hope that they do, at least.