There are several fixes since RDK 3.0 release to select correct Scaler coefficients in both SWMS and HDVPSS driver.
Can you pls check the same on DVRRDK 4.1 and see the quality.
For NSF I will share a patch to reduce Gaussian noise. Can you confirm you have NSF enabled and you are not just using it for Chroma format conversion.
Additionally share your Vsys_printDetailedStatistics on DVRRDK 4.1 to confirm low cost scaling is not happening in SWMS.