Fresh install, Dual Boot Issues

[GCWShadow]

I'm actually having experiences on installing 8700k build on High Sierra with dual boots (Win + Mac). But actually I'm not clear about how everything's work.

For now I have another build with 10700k + Z590 vision-G. Sadly, in order to make the OS compatible with my Nvidia 980 ti, this build is going to run on High Sierra again.

Anyway, I'm aware that nowadays the latest MacOS requires OpenCore to be the Bootloader for CustoMac. But how about a fresh install for older version OS, for example, High Sierra?

In addition, what is the best disk partition choice for Win + Mac boot?
In my previous build, I actually install the two OS on the same disk and then assign two additional disk for them as data drive (which are 3 disks in total). However, I truly hope that each of the OS can use the entire SSD and this time I have two SSD drive if needed, but I have no idea about how to make the Bootloader detect both OS on boot if the two OS are on separate disk.
Just seeking any solutions instead of manually switch startup disk in BIOS.

Thanks a lot for any comment

 

[Edhawk]

For dual booting macOS and Windows on separate SSD's have a read and follow this guide by @Going Bald - https://www.tonymacx86.com/threads/guide-multibooting-uefi-on-separate-drives.198869/

The guide is a bit old, but still relevant.

 

[GCWShadow]

Thanks for the nice reference!

Although not sure why this work, it definitely worth a try!