We have a 2003 Speedster with a WoundUp carbon fork. I really like a carbon fork. Our Speedster for sure has the Reynolds tubing. It is odd that they have different specs in different places for the new Speedster. A call or email would straighten that out. If the new Speedster is really CroMo, what does that do to frame stiffness? I wouldn't want to tour on a tandem that was less stiff than our Speedster.

With the Carrera, you'd want a different touring wheelset, but I think every tandem that's used a lot should have 2 wheelsets, since you can't just grab a different wheel off one of your singles. Of course the carbon fork precludes front panniers, but we tour with only rear panniers when fully loaded for camp-touring as we also have a carbon fork. Handling can be a little weird with only rear panniers, but we prefer it anyway because of the lighter weight.

We've toured with 28mm tires and an all-up weight of ~390 lbs. but I don't think I'd be happy with those tires and much more because we were out of room to increase pressure.

Many teams have had failures with Rolf tandem wheels. I don't know if these are different from the ones that caused the problems, primarily cracked rims. Your team weight might make the Rolfs a not every day wheelset. The Rolfs have an internal width of 17mm, so I don't know how they'd handle with a much wider tire. You'd want to check on max tire size with the CoMo carbon fork.

I've run both timing chains and Gates belt. IME there's not much to choose, really. I like the belt for touring because we're only dirty on one side, so easier to manage in hotels, etc. If it went out, it's easy to replace with rings and chain.