Howdy,
I have both the LCD and the BLUE/white Aquaero's to hand but not an OLED. Hard to say but for info I do notice there is slightly more play about 1mm on the LCD buttons compared to the BLUE/white ones.
I would imagine all the riser spacers are standard stock items, but without removing my LCD Aquaero I cannot compare the difference between the two, not that that may help with the OLED version.
Looking at the design if it is indeed thinner and you are unhappy with the gap the OLED could have behind the face plate keeping your orriginal spacers, then you would need new buttons and from 6 to 10 new riser spacers of various lengths.
I would just live the gap, or perhaps they come with them already.
SNIFFY