With prior Vegas versions I found that my best renders were when I Disabled "Resample Mode" and Deinterlace was set to "Smart".
With "Optical Flow" as now being a Resample mode option, what's the general recommendation in V20 for this setting? I generally film 1080p and render 1080p, but half the cameras in my multi-cam shoot film 4K (still for a 1080p render).