GC > Preferences > General > Selection > Selection Size
1) Position Color + Size Color

Ok as preferences, unlikely that you change this ad-hoc.
2) Display next to selection rectangle

Better in the main menu with a keystroke to toggle this on/off on demand.

Rename from "Size" which in general language means simply "width x height" to "Dimensions" which better corresponds to the fact that it also shows the co-ordinates of top-left and bottom-right of the selection.
Menu > View
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Show Selection Frame
Show Selection Dimensions
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