Nothing replaces aspect ratio when it comes to altitude performance, The Mirage was designed at the out set to be a high altitude machine (in GA piston terms). The TB-20 by contrast is a development of the 160 horsepower fixed gear TB-9 and as such not designed and optimised for high altitude. The wing airfoil as such has little effect, the 2300 series being used on everything from the RV series of homebuilds and Bonanza to the Citation jets.
The link provides a discussion about the elements influencing the wing design of an aircraft Peter Garrison both designed and built. He is a gentleman who knows about what he talks.
Wing Geometry