Some of he images seems like there is just a lot of clutter in the water ...and verified by the same clutter showing in the 2d ...
Keep the Sharpnes off and turn the Contrast down a little to see if some of the grainy will go away ...
Your Down Imaging is about normal for the HB SI units ...which do not have a dedicated "down pointing" piezo ... The DI image in the HB SI units is a computer generated blend of the left and right SI data ...
The line running parallel to the left of the center line is a reflection off something on your transom to the left of the xducer ... jackplate, another xducer, ladder, livewell screen, etc ...
Rickie