It works both in 3V 5V.
I use it with an Arduino Nano 3V and U8GLIB library.
I use the manufacturer: "U8GLIB_SSD1306_128X64 u8g (U8G_I2C_OPT_NO_ACK); // Display qui Does not send ACK".
This module is different from the same dimensions Adafruit with a reset pin. The Adafruit library does not work (or I did not manage ...).
The holes are of diameter 2 mm.
The screen is very readable despite the display surface of 22 x 11 mm