The different BIOS is to change BIOS settings - that's not going to matter with missing drivers. Plus, like you said, that's for a CR-48 - not a C720. I don't know how similar they are, but I wouldn't really risk flashing a BIOS that's not specifically meant for your hardware..otherwise you'll just end up with a nice looking paperweight.
According to the link I posted the following doesn't work:
Keyboard and Trackpad do not work.
Sound does not work.
Video Accelaration does not work.
Power Management does not work.
If you can find drivers for the C720, then by all means go for it. Last activity that was in the thread I linked to was a month or so ago, and they still didn't have all the drivers for it, because apparently none were made for Windows.