ok i'll explain the best I can.
TYC projectors really are not all that special. They are a projector plain a simple. But they are a halogen projector they were never intended for HID use. You hear TYC projectors and retrofits in the same sentence for mainly one reason. People remove the clear lens on the TYC housings to put onto their OEM housings for their retrofit.
Ok d2s bulbs are specificaly for OEM applications. That's why you see people using d2s/d2r bulbs in retrofits. They will not work in OEM housing nor the TYC projectors. d2s was primarly used by BMW in the beginning and d2r was designed for mercedes but alot of OEM HID equipped vehicles use them now. There are differences in the bulbs however in the base for fitment. The d2r bulbs usually has a stripe of paint on the capsule as well.
The shield provides your cut off and reduces glare in the projectors. Without that sheild your lighting would be **** bascially. So I wouldn't recommend removing it..you might be able to mod it but becareful. Then again it's ebay projectors your lighting output problems are simple. Their cheap made projectors with foglamp lens.
I hope this helped some.