Sensor Offset Question

How far from center of gravity does it become relevant to set the INS Offset? For GPS, I’ve set -7cm on the Y axis for the sake of RTK accuracy. IMU’s are 3cm forward on the X but I haven’t made those settings change yet.

Not very critical unless you’ve got a very large aircraft, maybe you’d do it if the flightcontroller was 20cm or more from the centre - bit of a guess though.

My flight controller is 33cm backwards from C.G point.i haven’t configured the INS offset but RTK GPS for Yaw measured with respect to C.G point.
I have to set FC offset too?

You set offset on all accelerometers, it should be INS or IMU something X Y Z

Do you refer with respect to C.G of the frame.

Yes, though any fixed point near actual CoM will be good enough. For copters frame center should be good enough.