I think it depends on which VSTi you are using. Superior Drums has enough controls built in to the VSTi that you could do everything there and send it as a 2 track to the main bus. EZDrummer doesn't. Although EZD is meant to just drag and play, as noted by others it doesn't sound great right out of the box and you need to massage the individual tracks to make it sound decent.
Even though Superior Drums has extensive capabilities, I still send the tracks individually to the DAW and use my UAD plugs on them. I don't know anything about Addictive Drums or SSD.
As for the canned groove files, I edit extensively. I like to use their files as a starting point then I edit the drum hits to match what I hear in my head. I love this part of writing drum tracks. I can spend hours editing drum parts.
But I have found that some of ToonTracks expansion tracks don't need a lot of editing. The Americanca expansion pack is one of them. I've only used it once, but I don't think I did a whole lot with it other than dragging the files onto the midi track.
Hope this answers your question.... Maybe I went off on a tangent.