I have some experience in making driver for 12W stepper motors for CNC router.
The classical scheme is the following:
L298 is used with L297, which implements all logic, and controls the current. To control the drive current It compares voltage at SEN1/SEN2 with voltage at VREF.
My stepper motor works at 1.5A. It have resistance about 2 Ohms. So, if you want to run it at constant voltage, maximum voltage is 3V. It is unreal!
If you control the current, you can run it at any input voltage.
I don’t know anything about small stepper motors, maybe there are motors, which can be run at constant voltage 5V or 12V.
L298 have inputs to connect current-sense resistors, but I have never seen an I2C board with this resistors.