The Finished Maps section of the Guild here ( https://www.cartographersguild.com/forumdisplay.php?f=36 ) has thousands of maps that can be useful as...
Cartography is the art of abstraction to fulfill a purpose. You may find that several simpler maps (or layers on a simpler map) are much more useful...
https://docs.qgis.org/3.34/en/docs/training_manual/processing/no_data.html might be helpful for using QGIS to add two layers and a constant together....