Would Xia, Shang or Zhou era Chinese people have worn modern looking Kimono type garments, or is that an anachronism we get from later Chinese illustrators (like how medieval Europeans would draw classical era and biblical people in contemporary dress)?

I'm not sure what you mean exactly by "modern looking Kimono type garments", but the kimono is based off the hanfu (漢服) if that's what you're referring to. Hanfu were around for a very long time...I know ancient sculptures and paintings will depict people in hanfu. Here's an example, it's a sculpture from the Shang dynasty that was found in Sanxingdui. I'm not a historian, just Chinese and reasonably interested in Chinese history (so there may be errors).