The warning is that the driveway and sidewalk cross over each other without being connected at a node. This can be a problem for routing engines, especially if it should be possible for a pedestrian to turn from the sidewalk onto the driveway or vice versa.
Both options connect the driveway and sidewalk, silencing the warning. The second option additionally turns that node into a Pedestrian Crossing (highway=crossing). Normally, the first option is good enough if the sidewalk continues uninterrupted past the driveway, but you’d use the second option if there’s something more substantial such as curb cuts or markings, like you might find outside a business.
(There’s an ongoing discussion about whether we need to somehow explicitly indicate the more mundane case too, but there isn’t a concrete proposal yet.)
I don’t think anyone is picky about the formatting. 
Around here, when you see preformatted text like that, or something of the form key=value, this refers to a tag. In the iD editor you’re using, you normally don’t have to fuss with tags, because presets and fields are available for all of the common feature types, but you can expand the Tags section of the sidebar to see the raw tags on a selected feature.