It should be nominate strigiceps there, and the map that Paul linked seems very accurate in my experience, though I've not been to Joaquin Gonzalez myself. Certainly Nacho is one of the most expert ornithologists for Argentina, and is based in the Salta/Jujuy area, so I would be shocked if the map weren't pretty much perfect.
Interestingly, though, the split isn't a clear yungas/chaco split once you're actually in that area, as the "Yungas Sparrow" (dabbenei) occurs mostly in the drier / scrubbier lower altitude parts of the Andean foothills below the Yungas elevation band. Personally, I've never seen it in proper yungas, but rather around 1000m elevation in scrubby chaco serrano habitat, and it certainly looks more like chaco than yungas when you're there.
The nominate form seems to occur from just about Joaquin Gonzalez to the east, and dabbenei (Yungas Sparrow) starts about 20-30km E of Joaquin Gonzalez, where the first hills start, south of PN El Rey. This outlying line of hills / small sierra is home to EcoPortal de las Piedras, PN El Rey, and is essentially chaco serrano vegetation up to about 1500m giving way to yungas above about 1600-1800m, depending on exposition, and it seems that the eastern slope of these hills is the eastern limit of the range of dabbenei.
I did a quick look for media on Macauley/eBird and there is one photo from Joaquin Gonzalez, but it's poor and the face is hidden - it still just about looks convincing for nominate, as expected. The rest of the photos that I was able to see from nearby sites correspond perfectly to the map that Paul linked above in the SACC proposal.
One other note - anyone who goes to this area, you don't even really need to look for detailed gen or select a specific site to find dabbenei. Anywhere within about 20km of the cities of Salta or Jujuy where you have scrubby chaco/monte type vegetation around 1000-1200m, you should find this species without much trouble. I've kicked up tons of them without trying while (not yet successfully) trying to actually see a Huayco Tinamou.