I have a similar setup Gigabyte z390 UD, 9700k, gtx 1080, high sierra.
So different gpu and running HS. Still some things you could try:
My shutdown was fixed by adding OsxAptioFix2Drv-free2000.efi to Drivers64UEFI.
I got igpu (UHD630) working on HS by adding some device...
Jiaiffe, Great that you got the TB3 to work with your board.
I'm curios, did you try any other firewire devices?
I want to do a build with the same board, but i have a RME Fireface 800.
Thanks is advance!
I saw some of your posts about the r9 280x.
I've been thinking of getting one (eventually maybe two)
I do a lot of FCPX.
Will two cards make a difference?
I've read about crossfire not working, but some posts are really old.
Also I've read that you changed the smbios to a...