Sandra, I got the 40cm width. I got my husband to carefully measure me over the back, shoulder to shoulder, and we eliminated a cm to account for some fat padding on the outside of my shoulders. The idea is to have the same width as would keep your arms straight in front of you- the same width as your shoulders.

And yes, you should EXPECT to feel sore in multiple places for the first couple of weeks of switching to a road bike from a hybrid. You are using muscles that you were not using before. Some people never get sore right from the beginning, others get sore in lots of places. Sharp bad pain or numbness is probably more likely due to the bike fit. Soreness can just be muscles being asked to do new things. I even found my actual reach has extended over my year of riding, probably due to muscles getting more flexible and my core muscles strengthening. My hands/fingers can stretch more now than they used to be able to, due to all the many hours they have stretched to reach my brake levers.

You have all the time in the world to get used to your bike and then slowly notice that something is not working well for you. DH emphasized this to me when I started out, and I'm glad i rode a long time before making various changes. I was then better able to judge whether some problem was due to my bike fit or just due to my body and muscles not adapting yet.