Photo 1 I believe is noise, soft focus and dark shadows.
Photo 2 I believe is noise, halos, magenta in sky and dark shadows.
Compositing is an advanced skill. Pixelated, low-res elements, jagged lines and noticeable halos don't work well. Everything should be seamless and organic. Otherwise elements look weirdly out of place with the rest of the scene.
PiXimperfect has a good beginner's tutorial on Blending Images and Creating Composites in Photoshop.
Hope that helps.