Also as far as boot screen goes, didn't someone recently find out that boot screen is on board now, not the gpu? on newer machines.
I think they found that the entire ROM for the card was on board.
I don't know how important that is. Doesn't mean cards still can't have their own ROMs (the eGPU ones still do), and it doesn't mean a new Mac Pro has to do the same thing.
I'm not sure how things are going with boot screen on newer computers. Newer Macs supposedly support EFI GOP, so in theory they should display boot screens on stock PC Cards for eGPU. But, haven't heard if that is working or not.