Success! I was really surprised that even wiping my system drive using Disk Utility didn't remove my EFI partition. That was my big worry / confusion!
For anyone who needs to do this in the future, here are the steps I followed:
1.
Downloaded High Sierra from the link in
this thread
2. Created a bootable startup usb drive using the terminal command:
Code:
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ High\ Sierra.app
Note: this will take some time; so be patient.
3. Restart your computer and choose "boot using macOS High Sierra install bootloader" from the clover menu.
4. After a few minutes, you are brought to the install menu, at this point if you try to simply choose "install macOS" the sytstem will not let you since "a newer version of macOS is already installed on this drive" -- therefore, choose Disk Utility.
5. Select your system drive and click "Erase" choose APFS.
6. After the format is complete, go back to the main menu and choose "Install macOS." You will be guided through the install process. This will take some time, so be patient.
7. The computer will restart, and then again select "boot using macOS High Sierra install boot loader" the installation process will complete and the computer will restart a third time.
8. Upon restart, choose "macOS High Sierra" from your clover menu. This should complete the process and you should be up and running.
Hope this helps.