the SRS is the entire restraint system,made up of many different components.
the RCM is the module that monitors the system
i cant remember exactly,but i think the RCM is located under the driver seat,gray box with two square black connectors.
i do reccomend disconnecting the battery when working on restraint systems
even though i rarely ever did in my 25 years as an auto tech(17 years for ford dealer) if the key is off there is no power going to the module.but still disconnect the battery for safety sake.
i do recall an issue on some models of the Fords where the wires would break or chaff right inside the connectors,so i would look closely at them,even give them a light tug.have seen the copper strands brake inside the insulation and the insulation was intact.
if the light is on(as stated) it is in default. all default is, is deactivation of the system.so no, no bags would deploy in an accident. and no the system will not deploy if the battery is disconnected. it needs voltage to set off the system.