But for FMA CAT I, it means there is no autopilot engaged, so the approach can't be flown automatically right ? So it is not linked to a CAT I ILS approach with a DH of 200 ft, it has no link to that (whereas for CAT II and CAT III it is linked to the CAT II and CAT III ILS approach with their respective DH)
You can have CAT1 displayed on the FMA with or without an autopilot being engaged, it is purely the approach status of the aircraft, if you lose one of the two ILS receivers the autopilot is still available but the land category will show CAT1 as you require both receivers for CAT2 or 3.
The minimum height to disconnect the autopilot on an ILS with CAT1 showing on the FMA is 160ft AGL, if you don't disconnect the autopilot FLARE mode will engage and the aircraft will perform an autoland followed by an auto roll out. It won't be legal but the aircraft will go ahead and do it. If you disconnect the autopilot CAT1 stays on the FMA, the flight directors stay engaged and will also enter FLARE and ROLL-OUT mode during the landing.
Basically it is quite possible, but not legal, to autoland with CAT1 on the FMA.