Hey Tony, sorry I got a little mixed up with the verse and chorus in my response.

I meant that approach for the chorus section -- Guitar 2 playing single strums while Guitar 1 plays the main bluesy riff.

For the verse, you actually had a good idea playing the voicings higher up the neck. That would sound nice and thick. You could also just have Guitar 2 double exactly what you are doing to make it sound huge as well.

so, in direct response to your points:

1) either would work great ... experiment and see which blend you like better.

2) the chorus is where I think single strums underneath that riff would sound pretty good. again, you could also have Guitar 2 jump in on that riff with Guitar 1 and add in the slide part along the way when needed.

3) no, sorry that was my mistake in my previous response. Whether you choose to play higher chord inversions or unison, make sure you are strumming and holding the chords for the same amount of beats on each guitar. This will give the tightest, biggest sound.

Hope this helps!
Mike