That's not what he means by project settings.
What are you putting into your editor? Lossless video in a codec like Lagarith or huffyuv in an AVI container? Professional-level "near lossless" codecs like ProRes? The unaltered Blu-Ray format of H.264 in an m2ts or MKV container? A ripped and reencoded Blu-Ray in H.264 format in an MKV or MP4 container?
What are your output settings? You say MP4, but that's a container that can mean many things. Is the codec H.264? H.265? MPEG-2? Are you using a set bitrate (like, say, 3000kbps)? Variable or constant bitrate? 1-pass or 2-pass encoding? Or are you using a constant quality encode, and if so, what's your CRF value? 18? 14? 22?
All of these things are important to figuring out why your quality isn't where you want it.