Ideally the UVs are arranged to be proportional to their corresponding faces or as close as possible in order to eliminate or at least reduce distortion. The 2D placement node’s default settings will cause the image to fill the 0-1 UV space so non square textures will be stretched. I did a video on its settings for another member. In short, the Coverage, Translate Frame and Rotate Frame control the scale, position and rotation of your image in the U and V directions so you can use these to set the image to the original or desired proportions. As for camera based projections, I’ve taken to using the planar projection instead with the camera option selected. The planar projection has the option of keeping the UVs proportional with the “keep image width/height ratio” check box, so I don’t have to fiddle with non-uniformly scaling the UVs so much.