Automation differences: host automation <-> midi learn

[EMC_Square]

Hi, I am always confused by the different controller assignment strategies and when to use what in combination with automation recording. Afaik, there are 3 ways:

1. Using midi learn in a plug-in
2. Enabling host automation and then assigning controllers via Ableton -> configure
3. Predefined assignments via controller surface in the preferences

First question. With regards to (3), is that the same as if I do (2) for the specific parameters manually or is it something totally different from (1) and (2). I never use it as I don't like predefined things in general. I have two controllers (Arturia Keylab essential and novation launchcontrol XL) and ableton automatically chooses them as controller surfaces and now I control parameters which I don't need to control. Is the best way to deselect them in my preferences or just overwrite them with strategy 1, 2?

Second, what is the difference between 1 and 2? When do you use which one?

Thanks a lot.