I have a Godox AD200 with an XPro-C transmitter. I would like to get my 430EX II to fire with it, off camera. Do I need to attach an X1R or an X2T to the bottom of the 430EX II to make it work with my setup?
You have to attach an X1R-C receiver to the foot of the 430EX II to use it in the Godox 2.4 GHz radio system. The X2T is a dedicated transmitter unit and cannot be used as a receiver.
Ideally, I would recommend that you consider getting a Godox TT685-C or V860II-C speedlight instead to use as your off-camera speedlight. It's more expensive than the receiver, but more convenient and robust for off-camera flash setups (they have a built-in Godox transceiver unit so you don't have to attach anything to the feet). Also, unlike the X1R-C, the TT685-C and V860II-C, if firmware updated, can be used cross-brand with Godox transmitters for Nikon, Sony, Fuji, Olympus/Panasonic and Pentax. So if you ever leave the Canon fold, you can still use those speedlights as off-camera TTL flashes over radio; all you have to do is rebuy your transmitter. The X1R-C becomes a manual-only receiver if used cross-brand.
Yes, you need to attach a separate receiver to the foot of the 430EX II.
The 430EX II has a built-in flash wireless slave system, but it will only operate with Canon's proprietary optical wireless system, and only when used with an compatible "Master" flash like a 580EX II, Canon ST-E2, or the built-in flash of some cameras like the T7i or 90D.