Indoor Drone no Mag State Estimation

Hi all,
I am setting up a small drone for indoor navigation applications:

Setup: PX4 v1.14, Holybro Kakute H7, Holybro PMW3901 Optical Flow Sensor, Holybro ST VL53L1X Lidar, NO GPS/MAG

I was wondering if it is possible to fly with the EKF2 state estimator with no MAG? I have read in the documentation that a magnetometer is required, but have also found the EK2_MAG_TYPE parameter which can be changed to None, and SYS_HAS_MAG which can be disabled. If it is not, does the Q estimator work, or should I switch to a system with a magnetometer?

In regard to optical flow setup, is there any other parameters I am missing to enable it?:
EKF2_OF_CTRL
EKF_TERR_MASK (set to default 3)
SENSE_EN_PMW3901
SENS_TFLOW_CFG

Lastly, it seems that EKF2_MULTI_IMU is set to 3 and SENS_IMU_MODE is disabledb, but as far as I can tell the Kakute H7 only has one IMU. Why would these parameters be set this way?

Thank you for the help!