I passed along a Reynolds 531 Mercian mixte I found, used, in Eugene, to an X-GF in Berkeley..

downside to using High end thin-wall tubing in the Mixte layout, was the head tube was relatively easy to torque
with the handlebars .. front wheel track could be moved sideways ..

She has an old asian made Gitane badged one ( from our Uni Time in the late 70's.)

the thicker tube wall . hi-ten steel was less noodly ..
even still in the Mixte twin thin top tube rear stay design, because they use more of It.

So IMHO the larger round top tube one would probably be better in that regard..

Then strip parts you dont like , put on those You Do..