What is difference between FCAB and FX0

Dear,

I don't fully understand difference between FCAB and FX0 when load case is cable stressing.

I know final cable element force is exact as the value of FCAB, but is not the same as the value of FX0.

However, why is two types of load case is needed in RM bridge.

Which case is needed by FCAB and FX0 respectively?

I don't understand that manual shows FCAB does not consider P-delta effect, large displacement.

please your explanation is appreciated.

Regards

Dan