Is there any video Hardware encoder/decoder open session limitation with Pascal Maxwell etc..

I saw encoder utilization in “NVENC_DA-06209-001_v08.pdf” doc page 9.
It the document there are Hardware encoding performance of H264 and HEVC in a different presetting,
But all the tests are done with: Resolution/Format: 1920x1080/YUV4:2:0, 8 bit .
For example H264 with preset of High Resolution and constant QP can do MAX 648 FPS (21 channels in 30FPS)in Pascal and gen2 Maxwell can do 430 FPS (14 channels in 30FPS.
My question is if I reduce Resolution/Format: lets say QVGA 320x240 instead of 1920x1080 then MAX open video channels will be grater than 21 in Pascal or 14 in Maxwell?
Or is there any open channels limitation for the different architectures (Pascal and Maxwell)?
Does NVIDIA have Encoder/Decoder Performance doc for different resolution than 1920x1080 ?
P.S. is there any intention to support VPx video Hardware encoding by NVidia?