I've read through many threads over the years, but don't think I've ever encountered a straight answer to this, or if it was there, I totally missed it. Let's say I upgraded to the Apple recommended Sapphire Radeon RX 580 Pulse. I know I would lose the bootscreen that I currently have with my flashed 7950. However, would the different startup options still exist if I booted with the option key, even though they are not displayed? Could I blindly choose to boot into Windows 10 or my recovery partition, by using the arrow keys and return to select my preferred startup disk? Or is is that, without a supported bootscreen GPU, those options simply don't exist at all and cannot be chosen blindly? If I know the necessary keystrokes, it seems that living without a bootscreen wouldn't be that much of an inconvenience except for perhaps the times I would misjudge and boot into the wrong place.