Demographics vary by cruise. Longer itineraries tend to have more French passengers. 7, 10 & 11 tend to be majority American with sizable amounts of Canadian, Australian and New Zealanders. Plus many other countries.
Dress code is Elegant Casual (men in trousers with button shirts, ladies in dresses or slacks & blouses). FOR DINNER. During the day, just not bathing suites in dining rooms.
We have been on 16 sailings and usually do ten days. We also like 11's (Cook Islands) and have done one 14 day Marquesas sailing. Seven days is too short. Marquesas is is great, but sea days are not always friendly to a small draft ship. It is at its best in lagoons of the Societies.
For us (you may be different), we spend little time on veranda as the upper deck is so close, so we spend all our time there. You will find many repeaters on Deck 4 (window stateroom).
Much disagreement about best month to travel. I am sure others will offer their opinions, but we tend to go in June-August. That is winter in the south pacific, but it is only about 2 degrees cooler and there is less weather. That means that the waterfalls might be less spectacular, but it is also a bit less humid. Next year, we are going in April. So...go figure. All months are great and all months will have SOME rainy days (maybe for an hour or two).
You can use shipboard credits for excursions. Sometimes if you book them ahead, they charge your CC. Check with PG to verify.
No Concierge perks like Regent (we had a Penthouse on the Splendor last year and got several perks).
Make a reservation for dinner in Le Grill and La Veranda (Lke Regent's Seti Mari) the minute you walk on board. You might be able to make another later in the cruise if it is more than 7 days.
Remember that it was a Regent ship during it's early years and many of the crew have been on board for much of it's 25 year run.
HIGHLY RECOMMENDED.