Each point has an Alarm Sub-object. What is the difference between Point alarm sub-object and Generic Alarm Points?

Generic Alarms are very similar to digital limit alarms; however, they have a few unique characteristics that are designed for speciation situations.
Generic Alarms are meant to have their messages and setpoints change quite more frequently. This allows users to use a single generic alarm point to handle a large number of alarms by having a different message.
Generic alarms are meant to be used in association with Logic points in the automation. So you can create alarms that are driven from a more complex logic.
Please note that from automation API, you can create and remove Generic Runtime alarms that they are created and removed during the runtime without any footprint in the database configuration.