I have the same setup (Z390 M Gaming, RX 580) and I cannot boot with 10.14.4. I was running 10.14.3 with no problems and now I get a black screen after the apple logo. No errors, just black screen. The system is running at the login screen (beeps) but no video. I'm going to have to re-intall 10.14.3 and time-machine restore. Stay away from 10.14.4 for the time being.