I have six tuners on my LinkPi. Three Onn 4k for ADBTuner, and three Roku 4k streaming sticks for Roku Tuner Bridge. When I had the framerates set at 60 fps for all, video was stuttering as it seemed to be maxing out the LinkPi's encoding capability. It was down to either lowering bitrate or frame rate. I did a lot of fiddling with both, and found that these settings allowed smooth video from all of the input sources.
I don't know if it's the right setup at all, since it was just derived by trial and error. From what I understand, "common frame rates include 30 fps for television broadcasts and 60 fps or higher for sports, video games, and slow-motion effects". I chose to split the difference between the two.