The drywall guy installed drywall around a washer box and a gas box that is recessed into the wall.
The edges around the recessed boxes are not straight.
How does one go about fixing this so it looks nice?
Home Improvement Stack Exchange is a question and answer site for contractors and serious DIYers. It only takes a minute to sign up.Sign up to join this community
Not the best workmanship I've ever seen, but most washer boxes like those have a trim piece with a flange that covers the drywall about an inch or so. Your drywaller probably knew this and didn't work hard to do neat work in an area he knew was going to get covered by by a trim piece. Assuming that's the case, this is no big deal.
Drywall hangers are paid for speed, and they rely heavily on talented tapers who can fix the occasional slip of the knife/rotary saw in mere seconds. However, if your hanger knew that you were doing the taping yourself, he should really have put in the effort to minimize this type of repair work. Also, the damage to the plumbing box is a little sloppier than I'd be happy with.
All this is very subjective, however, and I've voted to close the question as off-topic for that reason.
Regarding your bonus question, simply prefill with mud and overlay tape wherever the gap is larger than the trip ring will cover. Skim later to finish.