as a comparison, my Tricross has a toptube of 54.5cm , on a medium or 54cm frame. Although on paper I should use a larger frame at 5'10", this toptube length (and whatever effective tt length it has) and the stock stem (probably a 90mm) works great for me with the dropbars that are on it (diff bars have diff "reach", distance from tops to hoods)

a medium Troll has a tt of 570mm, a whole 15cm longer than my Tricross,
a small Troll has a tt of 549mm, very similar to my Tricross--BUT, I dont know how I would be on a small frame at 5'10" , it might be circus clown material here......

in my case, a med troll might work with a really short stem, but here we get into the unknown without actually putting one together and seeing--which is the worry when you get into buying only a frame and going the build up route. The same pretty much goes for the "small" option.

hopefully you can measure your road bike and compared numbers to the xs Troll and hopefully things match up closer for you.

Llama--neat Rawland bikes, but 3k Amercan, thats $4200 Can. ouch. (and not with the crankset I would want)

One thing with the Troll that is a known quantity is that it is a tough frame that handles a load really well. Like you, I'm never going to go nuts with overloading also because Im a skinny guy who learned a long time ago that keeping it to not much over 45lbs or so is pretty much where it starts to get not fun for me.

the horizontal dropouts on the Troll are something to consider re fenders, and specifically having lots of clearance to remove your rear wheel for a flat (as you have to pull it out far back) but I seem to recall folks on this forum in the past with Trolls saying thats its doable.

like you, a disc ready frame is what I would want also for this sort of bike, despite only having had canti and v-brake bikes, specifically thinking of riding a lot more on possible muddy gunky roads.

This VO Piolet frame is neat, but in my size, its 700c wheels....

a friend of mine in Vancouver bought a troll last year, stock, and one thing to consider is its weight. Perhaps look into if you can find reliable info about frame and fork weights compared to other frames. Given that you aren't going to overload a bike, perhaps there are lighter combos out there--although this gets back to my interest in this whole thing--what are there in 26inchers ??

cheers,