Image in New Card Visual (incorrect size)

In your case specifically, yes, if you set a px size then it may not be applying after GA. Using November Desktop, you need to change the Image Fit to "Center" to get that size to apply, and also reduce the Image Area % to 20% or so (it was likely undefined previously and now applies the default of 50% of the Callout container area).
The previous image settings were at the top level, but were moved under Callout -> Image.
There is a new "Image Hero" feature at the top level of the format pane now, this is a new Image that has it's own separate container (not part of the Callout container).