and what about the Libs directory? isn't that also for hardware drivers?
Nope, that's Devs:.
Libs: is for .library files - shared collections of functions to support programs. GUI toolkits (Gadtools, Triton, MUI), the standard file requester, the AmigaGuide logic, the ARexx internals, those are all libraries.
That being said, some hardware manufacturers did use Libs: for software support (toccata.library), but it's a software interface to the hardware in a slightly different way then a .device, I think.