Two identical monitors are AOC 24G2U and have FreeSync and 144 Hz. Does the AMD RX 5700 (PowerColor RX5700 Red Dragon) support two identical monitors with Freesync under Windows 10 and Linux (Arch Linux)?
not sure about your distribution Linux
WIndows 10 v 1909 can do 3 panels in landscape fine for gaming so running a pair of them should be easier on the video card
My RX 480 only has 2 DisplayPort headers and I detest HDMI as it is bandwidth starved compared to DisplayPort.
If you are using 1080p panels its not a problem, at 4K however DisplayPort is mandatory with higher end panels like mine.