...With VSTs, they are completely interchangeable. So you wrap plug-ins, all your old sets will use the auto map functionality if the plug-in is wrapped. It doesn't matter which is loaded. If you ever remove the auto map wrapped versions or delete automap entirely, everything continues to work normally...
The wrapper adds 24bytes/6parameters to every preset chunk saved with te wrapped plugin (when you save a project for example). Some/most plugins won't be able to read this modified preset chunk, when unwrapped.
The plugins are interchangeable. The plugin preset data is not.
Sorry I don't follow. Plug-ins presets have all been completely interchangeable for all plug-ins I've ever used. Both with Custom plug-in presets and with generic fxp/fxb. And for that matter Ableton presets as well. Also for other hosts I've tested like Kore, Maschine and Studio One. I have around 50 VSTs in my plug-in folder, not to mention the 20 or 30 I've sold since using automap. Every single one I save as an Ableton rack as a template and I save presets as Ableton racks. Regardless of whether I remove the auto map wrappers or whether I make a preset with either the original or the automap version, I can open projects and racks normally either way. I can open any preset bank made by anybody else when I'm using automap VSTs and I can share presets using automap plug-ins.
In short, I've tested every possible type of interchanging the plug-ins and the presets and I can not find any case whatsoever with VSTs where one can not read presets or existing settings within a project, regardless of what bytes are added. I'm on a Mac though, not sure if that matters.
AU on the other hand, yes neither presets nor the plug-ins are interchangeable. AU format keep the presets as a totally different plug-in. VST keep the plug-ins as the same plug-in.