Congrats - new bike day is always the best day.
+1 on Toshi's suggestion for a triple crank up front (get a light-ish road crank) with an 11-28 cassette in the rear - that's my setup on my long distance bike. That gives a wider gear range than the wide-low and minimal weight difference because the cassette is lighter. If you want to stick with the double, IMO the wide-low will not give you enough top end. You'll have to run something at least like the 42/28 (from Riv - but maybe wait for the lighter duty Silver2?) or the 46/30 (the "adventure" or "gravel" gearing available from many manufacturers) with a taller cassette (11-32 with most RDs, 11-36 on friction with most RDs, and up to 11-42 in friction with some RDs and maybe Wolf's tooth goat link) in the back.
I like using this gear ratio calculator:
https://www.gear-calculator.com/ Since you have existing bikes, you can enter your existing gearing then compare the gearing on your new bike. The gearing on your new bike should at least match on the low end and exceed on the top end of your existing bike. With a double that may not be possible so check what's the equivalent gear combination that low end is on your old bike, go find a hill, and ride it unloaded in that combo to see if that effort is something you can live with.
Also +1 on Toshi's suggestion for nicer tires: Rene Herse or Grand Bois, and I'd go for the standard casing for better flat protection.
If you haven't already, build up a nice light-ish wheelset. For rims, I suggest the Pacenti Brevet or Velocity A23 as good value options, with the latter available as an Off Center drilling for rear wheels. More expensive options exist of course. For hubs, the Shimano 105 is good enough but you'll have to service them periodically (and I'm not a fan of the bluish anodizing.) Rich built me an A23/A23OC wheelset with 105 hubs for my Roadini and it performed wonderfully.
Since you're going to be experimenting with bars and fit, I suggest investing in a "stem fit kit": an inexpensive quill adapter; a 31.8-to-25.4 handle bar shim; and a handful of inexpensive 31.8 threadless stems. Use Whatbars.com and your existing bike fit to get the range of stem lengths that would work. The Origin8 adapter is under $20. The Kalloy stems are about $25 each, and you can find them (and other value stems) used at a local bike co-op, here, in iBob, and eBay. IMO worth the investment since you're only going to know if the bar works for you if you go out on a decently distanced bike ride, and threadless stems are easier to swap than quill ones. When you're done, go get that nice Nitto stem for your AHH, tape and shellac your handlebars, and put these in a box since, well, n+1.
Since your riding position is changing, set aside budget for possibly a new, narrower saddle. I have Brooks B17s (170mm width) with my flat/alt bar bikes but use a GB Aspin (157mm width) with the cutout for my drop bar bikes. Some manufacturers and stores offer a saddle comfort guarantee, so check with those vendors if the need arises. I like to shop for saddles at
biketouringnews.com because they do offer a 90 day saddle comfort guarantee and sell a wide selection of saddles, like Brooks and GB as well as Ergon and WTB. (Not a paid endorsement - they've just been awesome the handful of times I've shopped with them.)
Looking forward to how your build ends up, with pictures of course.
--Ed C.
Redondo Beach, CA