What is the best solution for the default microphone and webcam on Mac mini M2?

Just about any popular USB webcam should work fine. I use my Logitech c925e and a Logitech H820e (DECT) headset with my M2 Pro Mac mini (some ones I used for the last 5 years on my old intel Mac mini). But I have also used my Samson meteor USB mic and my Bose 700 wireless headphones with the Mac mini.

So just about any USB webcam should be fine (use with either one of the USB-A slots, or get a USB-A-to_USB-C adapter), or any USB or wireless headset or microphone should work just fine. Web search from some reviews of equipment and find something that suits you and fits your budget.