You have pretty much answered your own question, if you use enough rudder you can maintain heading even though you will sideslip. When flying a track just adjust your heading to maintain the required track or let the A/P do it for you.
Using bank increases performance by using part of the lift vector to reduce yaw, hence requiring less rudder and decreasing sideslip angle. Less sideslip is less drag, thus increasing excess thrust and performance. Which is not really an issue during cruise.