Hi!
1. noisy shadows: select the light and in Attribute Editor ...LightShape -> Shadows -> Raytrace Shadow Attributes -> Shadow Rays (increase to a higher value)
2. skip render problem: in Render Settings -> Common -> Frame Range -> Skip Existing Frames (disable)
3. camera lag:
Disable some options in Viewport like:
Lighting -> Use All Lights
Lighting -> Shadows
Disable some options in Viewport 2.0 options /Hardware Renderer 2.0 Settings like:
-> Screen-space Ambient Occlusion
-> Antialiasing