firstly...I'd suggest that you run ddu in safe mode, to remove the video driver and install the most updated one. I think that will help.
I'd also have you updated the bios and chipset, I/O etc? check here
other thoughts... you could be pushing the PCEi lanes. with 16x gpu, and two m.2 not sure how many lanes they take but someone here might ...(I'd research this to know for sure) the z390 has limited lanes. Maybe test with only one (your o/s) versus both...
also the aorus mobo's tend to load slower for me I have the z390 xtreme.... I'm on a sata 850 pro... but the bios itself seems to take time to load vrs my other msi or asus builds.
lastly. are you overclocking cpu or gpu? ... your psu should be enough, unless it's very old or you are overclocking a ton. the 2080ti can be a hog depending on your volts.