We did this same cruise last year, the BA during Spring Break-this was our experience with our 13.5 year old teen dtr.
1. It was the 'norm' for bartenders to just make 2 drinks for you, at a time. Even the pool side waiters would come back with two of whatever you ordered.
2. We didn't do Vibe and I am glad we didn't. The DD didn't want to leave our side until the 4th day! She had no desire to check into the teen club. When we cruised with our 14 yo teen son, he checked in and had a blast. Girls are different.
3. Pool seats are gone by 9, usually. I found the upper deck that overlooked the pool to be fine for us, away from people falling on you or stepping on your stuff but close enough to hear the music and games. I had no problem finding a chair around 9-10am though.
4. GSC is lovely. We didn't do the villa's as it was just the 3 of us. There are plenty of seats and spaces there. It was there that the daughter FINALLY met some other kids and started to leave our side!
5. Understand that of all the thousands of cruisers that walk on the ship for NCL, only a tiny fraction of those come here to write reviews, and of those...even fewer write all glowing reviews. Your cruise with NCL is what you make it. I would join a bar crawl if your roll call is having one, we met some great people that way and connected with them throughout the cruise.