Successfully, installed Sierra over El Capitan on Gene with a M.2 NVMe installation drive. Here's the short story. (I'll update Post #1 soon.)
Note: The OP (Post #1) has been updated for Sierra installation procedures.
Update all your apps so you are current with El Capitan.
Backup your El Capitan installation disk. I use Carbon Copy Cloner.
Create the UniBeast installation thumb drive. This assumes you've downloaded Sierra installation app and UniBeast & MultiBeast for Sierra.
Copy MultiBeast for Sierra to the thumb drive along with other useful apps such as needed.
(Optional) To install on a M.2 NVMe SSD, you'll need Pike R Alpha's config.plist patch(es) as discussed in the previous couple of posts. (I'm not going to repeat them here for brevity's sake.) Copy Pike's patch into the installation thumb drive's config.plist. Then copy the patch to a text file and put it on the installation thumb drive to use later.
Boot into the BIOS and set the installation thumb drive to be the boot drive.
At the Clover Boot Screen, select the thumb drive and install away!
(Optional) If you're using the Nvidia web drivers, you should get an update notice after the installation is complete. Update and reboot.
Now, once you're back at the Sierra Desktop, run MultiBeast. Don't reboot, yet.
(Optional) For M.2 NVMe SSD users, mount the Sierra EFI partition, open up the config.plist file and apply Pike's NVMe patch as you did above to the installation thumb drive's config.plist.
(Optional) For Nvidia web drivers users, open up the config.plist file and apply tonymacx86's Nivida patch below and remove Boot/Arguments/nvda_drv=1 if necessary.
Code:
<key>SystemParameters</key>
<dict>
<key>InjectKexts</key>
<string>YES</string>
<key>InjectSystemID</key>
<true/>
<key>NvidiaWeb</key>
<true/>
</dict>
Now, reboot. You're done!