Does anything change when everything in the scene is doubled or halved in size?

Apart from the ambient occlusion in the world settings, that is.

So turn off AO, you make an animation, then you scale all x2 about the center? Will you get the same pictures? No.

Gravity. Subsurface scattering. DoF. That’s what I can think of off-hand. Probably lots of stuff.

Should it be possible, if you adjust absolutely everything, to get the same pictures? It should be.

Where can I find a complete list of all scale-dependant things?

For PBR, how many cm does one blender unit correspond to? I know it can be changed to display as 1cm or 1in, but does that display option actually change render behaviour?