in that video they are using a 3x1 PCIe expander card just like the one you linked too, the common Chinese ones are a bit unstable but you are missing an important piece regardless which expander you use. the BIOS needs to be edited to support that many GPUs. MSI won't formally support it with that motherboard as MSI did not qual that many lanes on the Z97 but you can hack it to do so, I didn't look close but I would hope that video discusses it because there is no way it won't work without a BIOS edit.