It depends on the juice. Some juices will scorch. Some won't. As to the heat - well, that's going to depend on your vaping style. Three or four short drags gets the outside of the carto fairly warm, but with the right juice it's a good vape. Chainvaping four or five long drags is enough to make it hot enough to be uncomfortable to touch the outside of the carto. And, that fifth drag is probably enough to burn the roof of your mouth a little.
Some juices I have I run around 4.2 to 4.4v with the 1.5 ohm DCs. A couple of juices I use are really nice on a 5.0v regulated mod. I seldom (but do occasionally) run the 1.5 ohm DCs at 6.0v