I have seen these 2 terms used when describing 80% unfinished lowers.

Are “Raw” and “In White” the same thing or is “In White” ready to paint where “Raw” requires additional preparation?

Thanks for any help you can give me. It would be MUCH easier to send off an unfinished lower to be engraved vs buying a black one, having it engraved then media blasting it to refinish it.

In the White typically means no finish is applied.

Your refinisher will need to prep it in any case.  I'm Cerakote certified.  If I do a finish that I'm going to be responsible for (i.e., if it starts flaking off, I'm going to redo it for free), I'm going to do my own prep, no matter what anyone else has done to it before me.  If I don't know how it was prepped previously, I can't be sure my coating is going to adhere correctly.