There ARE companions who can join you. We don't know how many of them there are though. And since the party cap is at 4, I *assume* that if you have the free slots, you can then bring them along.
There *MAY* be a new resting system in SoZ, but they are still testing it out. I assume if they don't like it, we would just have the same rests system that was in MotB.
?? I do not remember any changes in resting from NWN2 OC and in MotB, other than you could now rest until morning etc.. It was the same? As in you could not rest if enemies were near by, and a few areas (not many) were marked as you could not rest.