I'll add my experience to help anyone who stumbles upon this tread.
I have the same case, and I have 8 drives in the drive bay side, and several NVM SSD on the motherboard. With a PCle adapter to add sata ports.
I kept the original fans that came with the case, but then I was having cooling issues.
I bought a 5 pack of fans and added as many as I could. Adding 4 fans on the front, was the biggest improvement, with all of my drives dropping by 10 degrees.
I will be adding two drives on the motherboard side, but I want to try to find a way to add a fan under each drive.
A sleeper which OP didn't touch on, is that you can add 2 2.5" drives on the front panel. So I will be adding drive to use for my camera there.
So after this I will be left with 8 3.5" drives on the drive side, 2 3.5" drives on the motherboard side, 3 NVM drives on the motherboard, and 2 2.5" on the front panel.
But this will truly max out this case. Then I will need find a way to incorporate external drives.