I recommend straight posture! I have a few tips that are nice and easy to implement.
When you're drawing on a desk, either use a stand / easel, or if you don't have one just position your paper / tablet closer to you. That means you won't have to lean your neck so much.
If you have to lean forward, do it from the hip, instead of hunching. Don't curve your spine if you can help it. Try leaning so that your spine is still a straight line, in order to not irritate the upper part of it.
Having somewhere to rest your legs such as a footrest can help you maintain good posture. I tend to put my heels on the filebox under my desk so that my knees are elevated and my back is kind of pushed backward a bit. It kind of forces you to maintain decent posture and you're less likely to hunch.
As for stretches, my highschool sports trainers had a specific way of coaching it. You should do full 90 degree turns left and right a few times, and then lean your head forward and back in a similar fashion. Then, you should touch your ear to your shoulder on both sides a few times, and do neck rolls. Neck rolls are basically just dropping your head forward, and rolling it around to your shoulder to your back back and all the way around... You should hear little popping sounds (like popcorn cooking lol) as the tension is relieved. It's a good idea to do these exercises every day. You can find all sorts of neck stretches online, too.
I hope this helps??? At least somewhat.