I used to keep a pair of everyday shoes under my desk when I commuted.
I wouldn't want a carbon bike for commuting. I cracked a frame with a water bottle, it had a plastic lanyard that kept hitting the seat tube. It took a long time, it isn't like you'll give it a dirty look and it'll break, but working bikes see more rigors than purely recreational ones.
I'm comfortable on dirt with 28 mm tires. Most people prefer a little bigger. A skinny tire bike from 20 years ago
probably doesn't have clearance for anything bigger than 23 mm, but who knows? I second @
surak's advice about tubeless.