For all devices that have WHQL-signed drivers, those are the ones Bâshrat uses (even if newer, unsigned drivers exist).  Beta drivers aren't used unless absolutely necessary (as with nVidia's video driver because they suck lately ).  There are rarely exceptions to this rule.  Customized drivers from 3rd parties are never used. Period.

For devices that never had properly signed drivers, the latest known drivers are used.

The check for signed drivers, however, is not disabled permanently.  Disabling the WHQL check only prevents warnings with any unsigned drivers it finds that it must use (signed drivers will still be preferred over unsigned ones).  The check will be reenabled after Windows has all the drivers it needs.