My best friend was lucky enough to win the DEH lottery on Sunday, July 2nd for the 3pm show! We found out the results at 9am and bought the tickets within about five minutes. There was no indication if they were standing room or seated. When we picked up the tickets at the box office just after 12pm, they already had all the lottery tickets printed, and the name of the person who won was printed right on each ticket, so the time you arrive at the box office has no bearing on what tickets you get.
We ended up in the second row of the box on the left side of the audience (there's no seating on the box on the right side--sound equipment there instead). There are only five seats in the box: four of them are along the curved outer edge of the box and seemed unobstructed; one seat in the second row (mine! my ticket says Box50, LA 3) was partially obstructed by the person in front of me. Since there was no one behind me and the chairs are movable, I just shifted side to side or leaned as necessary. Again, I think my seat was the only one in the box to have this obstruction issue, since everyone else is arranged along the outside of the box and therefore has no one in front of them.
The tickets say partial view, but I didn't feel like I missed anything major. I couldn't see the band (stage right) from where I was, but my friend, who sat at the edge of the box, could see them at least partially. It was tough but not impossible to see Connor's mom when she was far upstage right during "Requiem" (the person in front of me had to lean right to see her). We couldn't see Ben's face during the first half of "Words Fail" since he's looking stage left (he turns to face the front halfway through the song and then we had a great view); we also couldn't see his face during "So Big, So Small" (but had a straight-on view of RBJ's face, which is the perfect view for that song).
Ultimately, I thought the seats were AMAZING. SO close with only minor obstructions (if you're stuck in the middle seat like I was, most of them can be fixed by leaning, moving your chair, or nicely asking the person in front of you to scooch a bit). Ben spends a lot of time stage right and our view of him was stunning. The box is also a great place for watching other people in the theater try to surreptitiously wipe away their tears
Long story short: we weren't told where our seats would be when we won, but we bought tickets quickly after we were notified and ended up in the box seats, which were great. If you want to guarantee a seat, my experience suggests that you should buy quickly! :) Hope that helps.

re: cancellation line: there was NO ONE in the cancellation line on Saturday, July 1st at 5pm for the 8pm show (or for any future shows), and the woman at the box office said it was likely that tickets would become available. We heard the next day that Ben did not perform that night, though, so that may have kept people away if it was announced beforehand. I asked the woman at the box office about SRO and she confirmed that they're all sold through the lottery now. I asked what happens to unclaimed SRO lottery tickets, but her answer wasn't clear to me. It may be worth calling the box office to ask if unclaimed SRO lottery tickets are sold to the cancellation line (like how Hamilton sells unclaimed lottery seats to the cancellation line at full price).
When we picked up our tickets on Sunday, July 2nd around noon, there were maybe 15-20 people in the cancellation line. Not sure what time they got there or if they got tickets.