We also tour on our Speedster. Works great. As above, only thing is that we choose to use fast road tires because we ride 99% on pavement. Our adventures onto farm roads with potato sized rocks and on cobblestones were not wonderful, but we survived with no flats or damage. We have been on one gravel road which had bad washboard and we had to turn back and find another way. My stoker had shaken baby syndrome. I think only full suspension would have made it rideable. We have been on gravel roads with very steep pitches which we did not have the traction to climb and thus had to walk, which was not good.
We know two tandem teams who toured extensively with a trailer. They much preferred that. OTOH they are strong teams who could climb OK with the added weight. Seems like steep gravel pitches might be problematic with a trailer. Our tandem rides much better unloaded and we love the feel of it. At speed with panniers it's fine too, but standing or maneuvering at slow speeds is not good. We'd still choose panniers because we would have trouble with the extra weight and drag of a trailer.
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