I processed a video with Premiere Elements 2019. The original video is a Full HD (1920 x 1080). Viewing it full screen from the timeline, the video is of excellent quality. After exporting to the PC, keeping the same resolution - MP4-H.264 format; I dragged the quality bar to "high". Unfortunately, the possibility of intervening on export parameters is almost nil. After exporting, I played the video from the PC and the quality deteriorated significantly, especially the scenes with camera movement (zoomed and panned) have a "liquid" effect like ripples of water; I don't know if the term is correct. I wonder what it can depend on? Thank you
Another possibilty is the camera's image stabilzation.
I have "Full HD" camcorder that was "top of the line" when 1080p was also "top of the line". When 'zoomed in' on a subject and then panned the video was mush due to the very good image stabilzation in the camera. To get the mush to go away I had to turn off the stabilzation or put it on a tripod.