There are actually smartphones and laptops where you can close the camera with an integrated sliding window. I don't know of such a thing for integrated microphones, but Thinkpad's bios allows disabling mic and camera, though if you don't trust bios's software switch, I'd recommend pulling the internal cables. Then you can connect a USB headset and/or camera on demand, knowing there's no always-on mic.

But, since even Windows desktop edition has Cortana these days, I'm afraid mic will be harder to disable in newer machines.