I talked with @Montellese on IRC and we for now don't have a "get default value" function. Also settings that are not display cause they belong to expert instead of Default is a problem.

I got my "nightly sleep" back, cause of the following: We don't hide VDPAU or VAAPI which is the parent of those two. So maximum that can happen is:
Use has intel hardware && installed the broken vaapi to vdpau wrapper && has VDPAU enabled && the decoder really opens && he complains that e.g. vdpau mpeg-2 or vc1 is disable _as_ he before had an AMD OSS VDPAU computer that could display those :-)