Oh yes, those large driver packages may include hundreds of files but the only ones used are the ones called for in the matching HW_ID line of the .inf file. Used to be before driver signing it was common to edit this line to install drivers that were close enough.
Typically, OEM hardware is sold without the usual warranty (the OEM self-insures in exchange for a lower price) or driver support beyond what is initially supplied, so it's up to the OEM to test later drivers and verify they work properly before posting them up on their own website. But AMD has been very good about including HW_ID for OEM products in drivers for all of their non-mobile stuff so usually their standard driver just installs fine.
Mobile was sometimes a little different because before every CPU had an IGP and the GPU actually used that IGP to render the final output, there were all sorts of proprietary ways to switch between the IGP and GPU to save power, and often the OEM had to modify the driver package to make that work. If you only had an IGP or a GPU in your mobile device then this was not a problem and usually the standard drivers work fine.