Yes I got official notice of this (I am a member) and it was accompanied by various videos of the build sequence. Apart from the plastic surface it looks a nice little stadium. Be interesting to see how it copes with the prevailing winds though but they must have thought of that - you would think!
To answer your questions - it meets the Pro 14 requirements. It is built so that it can be extended. Edinburgh have, I think, pre-covid about 5K STH so the ground size was chosen to get an atmosphere. If Edinburgh get into Euro competitions then they can choose there ground to suit - 7.5K or or 67K. The benefit of being fully owned by the SRU is they have two stadia to play with. Yes exactly like Leinster.
Being up there with Wasps just over a year ago was an experience in a basically deserted Murrayfield.