they're already integrated into one or both of the boards on the i2c bus, so i don't know how i would go about modifying them.
Yes they are on the PCA9685 board pulling up to the board's Vcc.
So if you want to use this board at 5V and yet drive it from a 3V3 system then you need either to:-
- Add an I2C level shifter board.
or - Unsolder them and add external pull up resistors to 3V3