Yesterday I managed to install High Sierra 10.13.3 (APFS) onto the 8300 SFF. The ride was a little bumpy, but smoothed out. After installing Nvidia Web Driver .152 (.156 wasn't good, it said something about I don't have the latest macOS build, which is strange, I downloaded it a week ago) I switched to it (from the active native driver) with the Status menu icon (asked for password) and rebooted, but the dGPU was still not active. So I got into the Settings, unlocked the lock icon in Nvidia settings and then chose Nvidia Web Driver. After this it worked.
About the theme thing: well, to be honest, I didn't bother with it. MultiBeast's Clover install works well with the built-in (non-tonymacx86, no matter what I set in the config.plist) theme. Actually, I see it rarely
What is left:
1. Generating SSDT.aml for i5-3470S
2. Setting SMBIOS stuff with Clover Configurator
3. Setup macOS and applications
I followed your YouTube guide, the quality is superb (may I suggest to implement when to restart?), but you also need the written part (SSDT generating and the CC/ACPI/DropTables settings part missing from it) to get macOS working properly. The written part does not contain the deletion of the hidden folder and file at the end of the video.
Many thanks for the guide!