I have the 055Pro and I find that it is a bit long (24 inches) and heavy. I am considering to get a lighter tripod with shorter folding length. This way I can checkin together with a small luggage.
1. To get a tripod bag or not - I find it helpful when carrying but when I start to shoot - I need to pack away the bag. Sometimes it is better to just carry the tripod by hand so you don't need to zip and unzip. Think of it as a "weights" - same function as the 70-200 or 80-200 zoom. Which is to increase your arm muscle.
2. Depends on what your trip purpose is - I find that carrying a heavy tripod can be a strain even with the bag if you go on a long hike. If you are mostly taking public transportation, riding, it should probably be fine. My purpose is to shoot long exposure shots when I travel. So I don't really like to bring long tripod in my luggage. If the primary purpose of my trip is to take pics, then I will bring my tripod especially for sunrise and sunset pictures.