Battery charger/power supply question

My caravan has a solar panel and battery with a prostar regulator. The main 240v power supply and 3 stage battery charger is an Electro brand (no further info in the manual). There is a switch to run this unit as a 3 stage battery charger or as a power supply. I find the manual confusing and need to know the best setup to have this switch. In power supply mode, the charger works as a 2 stage (bulk & float) and the manual states that this mode is intended for use to charge a battery with external load such as a caravan. I have another swith for battery type (gel, wet & calcium). Should an AGM battery be in gel setting? Another switch is for float voltage selection (13.2, 13.5 & 13.8v) Again what should an AGM battery be set at. Can anyone please explain the best setup to have for this unit when connected to 240 mains and when no power available. Thanks