Would the delay be only on the monitor connected to the USB graphics card?
If so, then that monitor could be used for a browser window or other non-trading app or charts not related to scalp trades.
Yes, monitors that are connected directly to the video card will have no delay.
I used to have on USB - VGA video card and there was a small delay, usable for browser stuff, not for watching videos or if you want to do scalping.
Maybe with USB 3 this delay also became smaller, i never tried one with USB 3 since i don't need to anymore.