Neither the arm warmers or the bolero take up much space......... I know, when touring, the idea is to travel as light as possible, but it might be worth it to take both. Wear the bolero with sleeveless tops and the arm warmers with ss tops. You might want to have at least one ss top with you. Gives you one more option, if needed. Will you have both front and rear panniers? Carrying sleeping gear? Cooking gear? It all makes a difference in how much room you have for "extras."

Personally, I like to take clothing that can be worn while cycling and while off-bike. Wicking fabric, but not necessarily bike jerseys on top. (I do always wear bike shorts, for the comfort, but usually with a skirt over.)

SR