I am new on hackintosh build also, my opinion is worth to upgrade 7700k with Z270 mobo.
I just success build with my rig. I am so concern about the audio ALC1220 and today solve the problem.
Ethernet still not work but I can use wifi, so that is not big deal.
Hello, as I have same Mobo GA-Z270X-UD5 with you, CPU i7-7700K, GPU GTX 1707. I have problem on Audio and Ethernet, would you please share how make them work. I just use Unibeast 7.1.1 and edit config.list and Multibeast 9.1
I just build GA-Z270X-UD5 with i7-7700K yesterday success.
Use latest Unibeast and Multibeast but need to edit config.plist file provided by kris33.
Refer : https://www.tonymacx86.com/threads/gigabyte-ga-z270x-ultra-gaming-and-ga-z270x-ud5-pictures.214622/page-2#post-1439481