I feel your pain. My kitchen remodel waited a month while I wrestled with such decisions, and it's a small room. Having always lived in houses with a single two-bulb fixture in the middle of every room and depending, otherwise, on floor and table lamps, it had never occurred to me that lighting decisions could be so complicated. I found the topic so absorbing that I've kept reading and thinking about it even though my kitchen lighting is long-since taken care of.

Even more so than with other types, the quality and amount of light provided by recessed lighting is determined more by the bulbs chosen than by the fixtures. If you know what sort of effect you are going for, if you can picture the light falling on a surface in a particular way, you can work backwards from there. Is the light direct, arriving at the surface in a direct line from the bulb, or is it indirect, having bounced off of a wall or the ceiling? Is it diffuse and soft-edged, or is it crisp and dramatic like a theater spotlight? Where must the fixture be positioned in order to put the light where you want it? If you can clarify these sorts of ideas then you can home in on the right sort of bulb, and then the fixture choice becomes much simpler. That said, 6" line-voltage cans are likely to be a perfectly workable choice. You could probably get away with 5" with the 10' ceilings, though there seem to be more trim choices available for the 6" cans. 4" would be too small except for accent lighting.

I'm not much for DIY TV, so I'm not familiar with Divine Design or the specific lighting you're referring to. If Candice is using these lights to illuminate something on the wall, such as artwork hung there, then I'd guess the lights would be at least a couple of feet out. If the lights are intended to highlight surface textures of the wall, they could be positioned quite close to it.