I’m contemplating getting a quantity of blank 1u keys to customise myself for the top row and side block of the f122. Are the keycaps actually different profiles, or is the key profiling actually achieved just with the bent metal plate?
If the former, how would I specify what profile a blank key should be in to match the rows in the left block to the rest of the keyboard? Or am I talking nonsense and it’s not this complicated?
All Model F and Model M keys are the same profile, so they can be used on any row (of course the different sized keys will only fit where the barrel spacing allows it – for example the right shift key only fits in that spot). The reason is as you say, due to the curved plate inside the keyboard. So you can order the blank keys or any of the Extra Keys or transparent relegendable keys to fill the F122.

Hooray for simplicity!