I'm not familiar with the different brands, but it is a heavy layer of a tan colored caulking. They even caulked where the awning attaches. I wanted to remove it, but looking at some other threads, it seems like other owners also have a lot of caulking on their roofs. It that the norm?
Usually you want to use Trempro-635 for areas where there is much of a gap or where you have to cover large areas. Parbond is good for around windows and it is thin and if applied correctly it won't look bad. Everything should be sealed because Airstreams tend to have leaks, yes even the new ones. Another place for leaks is where the bumper plate meets the rear of the trailer. You need to get all the old stuff off which will be a challenge to not damage the clear coat. In really gummed up areas paint stripper works well but it will take the clear coat with it. There are caulk remover attachments for drills with little plastic wings what are supposed to do minimal damage to the metal underneath. Post some photos so we can see what you are up against.
I just used a tube of Sikaflex 505UV (in white) on my roof. I read elsewhere here on the forums that it has replaced the 721UV. The 505UV is good stuff. I also noticed the factory store is not selling the 721UV any longer, but they are selling something called ADSEAL. Russ
Russ and Linda
2017 Flying Cloud 30'
2012 F250 Powerstroke 6.7