If you can get a field camera with a longer bellow draw at the price of the Graflex get it otherwise there is nothing wrong with buying the Graflex. For portraiture you don't need the sharpest lens, old single coated ones are fine. Film backs are more or less universal, there even exists a six sheet holder for the Graflex the Grafmatic, if you buy one make sure that none of the inserts has bend corners.

Good luck