The "rope" for all attractions will be the same location.
It can be
A. just before getting to the "under passageways" below SSE,
-or-
B. (as you mentioned) the area to the south of Fountain of Nations, just before the pass-throughs of Innoventions to the east and west FW attractions.
When they "drop the rope," guests will proceed to any and all of the open attractions (including FEA/Norway) at once.
What time do they open the gates?
Anybody's guess.
Be through security (which can be a chore to time)
and at the gates by 30-50 min. before posted opening time.
It's better to arrive far "too early,"
than it is to arrive one minute "too late."