I have a map made from vector layers and when I compare my map to the same area on a map produced by a commercial map maker, my map is stretched horizontally. The commercial map measures 30" x 25", my map of the same area measures 30" x 18"
I made maps from the same shapes file in both QGIS and ArcMap and both maps look the same.
I don't know if this influences the shape of the map but, the Reference System Information from my map data is: Code NAD83 (EPSG:4269) Codespace EPSG
The commercial map is NAD 27