Thanks for all that photo collating. I'm too lazy for most such work.
I agree a lot of transformations in the movies between Transformers (2007) and Bumblebee were lazy and just whatever the designers felt like. I was particularly appalled by the pixelated morphing of the fake Earth Transformers in Age Of Extinction.
As to scale - I'm happy overall with its presentation in Bumblebee. Most of it happens too fast for one to be bothered by any imperfections (and I do think they exist - pretty sure Bumblebee shrunk in robot mode a lot of the time to fit a scene).
For toys my own preference is for what I call 'scale ranking' rather than absolute scale. A plane and a car can be out of scale as long as the plane is still somewhat bigger than the car (as well as taller in robot mode). As with many other things this is a product of my G1 conditioning.
I wish there were two size classes within current 'deluxe' to accommodate this. I should possibly start my own post on the thorny topic of size classes...