How to do IMU and camera "sensor fusion" tracking?
Begin by finding a way to convert SLAM or ArUco data into absolute position in some coordinate system. This is most complex part and I have no idea how to to this, never have worked with either.

Then apply Kalman filter to accelerometer and position data, exactly same way as it is done for gyro and accelerometer (there are plenty of examples for that on the web, including hundreds of videos on Youtube).

The idea is to integrate accelerometer over time twice to get speed first and position second. The result would be fast position value with severe drift. Then you apply noisy and slow absolute position from camera to correct that drift.

This is the same as integrating gyro data to get fast angle with drift and then correcting that drift with accelerometer/magnetometer inputs.