Q1: If things work like 2015 with regard to Hall
D23, and so far from all appearances it appears they will, then yes, the morning and afternoon Hall D23 lines will be in the same place. Hall E downstairs.
I cannot remember from 2015 how afternoon queues worked. In 2011 and 2013 they would start another line for such things if the previous queue and not cleared yet. So a queue waiting to go into a queue.
Q2: In 2011 ands 2013, I arrived early each morning. I cannot remember specifically but generally by 6AM plus or minus 30 minutes. In 2015 on Day 1 I made a huge mistake and arrived about 9AM because the thing of primary interest was the afternoon Hall D23 Animated Films session. We waited outside in direct sunlight for 2 and a half hours. There were a whole bunch of queues outside at that time and we were sent to this queue which was to follow I believe three other queues which were before us. Once queues 1-3 were in and our queue started to move, the movement of our queue to the Expo entrance by the Expo organizers was handled improperly and the people at the end of the queue who had just arrived were allowed to rush forward in front of folks like us who had waited in the hot sun. I was ready to burst with anger. Not a good way to start a Disney Expo!
We easily got in line for the afternoon Hall D23 and actually got very good seats - we were far forward in the queue - maybe #1000 out of 7000.
Bottom line for me is I will only go to the Expo at 6AM or 11AM in the future. If 11AM, I will know I will be behind many thousands of folks. But in general I am planning 6AM for all 3 days this year.