Regarding the Ritchey Outback: They are rated the most compliant. But there is a point at which compliance becomes noodlness. Where that line is, I'm not sure.
As for me, I went with Rodriguez Phinny Ridge Bandito with the ultralight ThermLX steel option. Which is basically comparable with Reynolds's 853 & the top tube is undersized but then drawn to a different non-round shape for strength. The 200 gram penalty (1946 grams) is largely in the chainstays for lateral stiffness. Still, not bad for a size 57 frame.
To that, I added Stan's Grail rims (300 grams each,) an Ax-lightness Ergo 4200 handlebar, & Leaf Plus saddle, a Darimo seatpost & Sub 4 gram clamp, Extralite headset, spacers & stem. CarbonWorks bottle cages.
I'm still waiting for Extralite to offer their HyperRear3 hub before I build the wheels. Hedging my bets: I'm also waiting for a White Industries hub. Whichever arrives first gets to be built.
It has been 20 weeks since I ordered the THM Clavicula SE crankset. So, in the mean time, to make the bike rideable, I installed a Quarq D4 & some Mavic Aksum wheels equipped with Shutter Precision dynamo & Powertap hub.
I intentionally gave up 150-200 grams to use a WoundUp fork that allowed 180mm rotors. This was to be made up with Gevenalle shifters, but unfortunately, they had a parts shortage on hydraulic post mount availability. A used set of heavy AF Dura-Ace 9100 hydro/mechanical's mated to XTR calipers is what I settled on.
The bike is 20.3 pounds as ridden with pedals, but will easily be sub 17 pounds with the wheels & crankset swapped to as intended configuration.