You can do radiant under wood floors, you jsut operate it at lower tempratures. But in a cooling dominante "green grass" climate like Atlanta area, I don't think it would be worth it sie your heating season is so short.

If it takes a GC or drywallers 6 hours to cut and repair the wall, you money ahead if you spend about 2 fewer hours installing the furnace.

Bathrooms OTOH are great to have heated tile floors year round for comfort. But since they are small, it usually most economical just to use electric.