This video is instructive. While folks generally try pretty hard to hold a straight line on group rides and people generally ride directly abreast but in races all bets are off so do not overlap wheels. You can't always be exactly abreast of the guys next to you but recognize that there is death zone between a slight overlap and where you are far enough forward to put an elbow into someone's hip if they start moving over on you. There are lots of points in a race where you either need to go backwards or forwards because staying where you are is risky.

https://www.youtube.com/watch?v=BJr69MBg6-U