I just installed a GT 1030 (MSI GEFORCE GT 1030 2GH LP OC) in my system as well, it is also not great even compared to the previous GT 730 it was using, despite being more than triple the PassMark rating. The audio over HDMI is also a bit delayed, which was something that I did not experience with the GT 730. I have enabled/disabled/enabled the NVidia drivers and confirmed that they were on/off/on in the system info dialog. The NVidia drivers are definitely better than Noveau, but still not what I would expect. I booted into windows on the machine and ran the PassMark benchmark tool and got the ratings I would expect, so the card itself seems fine.
Is there anything else I am missing to get expected performance out of the GT 1030? I am running the latest stable release of Batocera (29).