olikraus:
U8G2 Library - Way too big! Didn't spend much time here.
At least U8x8 API should work. Also: I2C OLED will will use lesser ROM than SPI OLEDs (due to a problem in the Arduino Softare).
Oliver
As I understand, the U8G2 is a graphics version and writes to a buffer.
the U8x8 does not, it send data right directly to the display.
as for chips, take a look at the tiny ESP8285 w/1 mbyte flash.