The Chinese ranges that 1st Corps sell ( Shang, Warring States and Han) were originally sold by Curteys Miniatures and are in a different style to their other ranges. I don't have the Shang but do have a Warring States army and believe they are consistent in scale. Taking a sample infantryman he seems to be 27mm foot-to-eye ( 30mm base to top of head), and matches well height wise with Foundry and Aventine. The cavalrymen sits on his horse about 41mm foot-to-eye, and he is noticeably smaller than a comparable Aventine cavalrymen. Looking at the two Curteys figures side-by-side the actual cavalry figure looks a tad squat.
IMHO the sculpting style is quite distinctive, almost caricatured, and I wouldn't mix them with other manufacturers in the same army. That said not many other people make these periods so you will probably have to use 1st Corps/Curteys if you want a Shang, Warring States or Han army!