Option 3: This last option is a simple handoff; Lightroom hands the source RGB file over to Photoshop, without touching it in any way, and it doesn't try to track the results, either. So the results of using this option are identical to opening the file in Photoshop from the file system. Having the Edit Original option here in Lightroom is simply a convenience.
Having said that, I find this last option frequently to be the most useful, and that's precisely because of what it doesn't do. Reading the fine print again confirms that when handing an RGB file over to Photoshop using this option, Lightroom adjustments won't be involved. The beauty of that behavior is that it opens the door to the full power of using Photoshop and Lightroom together.
For example, let's say that you take a RAW file over to Photoshop for editing, maybe to add some text to it, or to add any number of other layers. Simply saving that new, layered RGB file in Photoshop also tells Lightroom to import it into your catalog. And once back in Lightroom, you then can apply any number of nondestructive adjustments to that layered file that you wish. Make it brighter, make it darker, crop it—whatever. Just understand that you're effectively applying nondestructive edits to the entire composite, layers and all.
Then, later, what if you need to change the text? No problem! Just choose Photo > Edit in Photoshop, and using the bottom option to Edit Original, make whatever edits you like in Photoshop again. Back in Lightroom, all of your nondestructive edits will still be in place, and Lightroom will update the preview to reflect the new Photoshop changes the moment you save it.
And so, grasshopper, this brings us back to the question that I asked at the beginning of the article: How do you know when to apply nondestructive changes to your RGB files in Lightroom, and when is it better to make them over in Photoshop?
When you know the answer to that, you will have truly snatched the pebble from the master's hand. But if you write to ask me what the answer is, I won't have it! I'm still working on that one, myself.