QueryIOSurf works in h264_enc_filter sample (CEncVideoFilter class), but failed with MFX_ERR_INVALID_VIDEO_PARAM in sample_vpp even if exactly the same (bit-to-bit) mfxVideoParam is used. Soft or hard - doesn't matter.
Using your sample_vpp command line and replicating it here on my side it looks like the issue your encountering is due to using input surface type RGB3. This surface type is deprecated and not supported anymore (the sample usage description unfortunately still lists RGB3, this is a documentation error).
If you change your command to use for instance RGB4 (-scc rgb4) it should work fine.
As I see, Intel VPP supports nothing CC conversion except target is NV12 and source is YV12\YUY2. Where can I find the list of supported modes?
PS. What <mfxInfoVPP::ChromaFormat> is intended for? It seems to me VPP just ignore this field.