I have a pixel 6 which is very similar to the 6a. I bought a vinyl skin to cover the back of the phone from scratches, and a cheap screen protector which I replace every few months. The case I got is a Spigen clear case which I like because you can see the skin under it.
I chose to add a skin because I wanted to protect the back of the phone from scratches, including the camera bar which is usually left bare. On my last phone the glass back got scratched by the case itself, so the skin helps a lot.
I don't care much about the screen protector because it's going to get scratched anyway, so I just try to find the cheapest ones I can. That way I can replace it more often.