Hmmm, interesting thread. Remember when looking at using your DVC points, remember your breakfast is covered as a part of the deal.
I have stayed in all the DLP hotels a number of times, as well as Dixie Landings, AKL, WL, the Grand Fla, the Poly and Contemporary in WDW, and the DLH and Grand Californian in DL, so if I can answer your questions I will.
All the rooms at DLP are smaller than even the value resorts at WDW (remember the ave 3 bedroom house in Europe is about 950 sq feet), except the 5 person rooms in the
Disneyland Hotel.
Personally I have had 7 wonderful stays at the Sequoia Lodge and 3 sub par stays at Newport Bay Club (inc in the admirals floor). The NBC is the largest hotel in Europe and has the staffing levels of the much smaller HNY (which offers much better service and ameneties than NBC and SL). so I would steer you towards the SL Montana Rooms personally.
SL and NBC are moderates by WDW standards. Only the HNY and DLH offer the service levels associated with the american resorts. If you go with that in mind, you will have a better time.
Bear in mind that the Euro vs the dollar is a big diff. To help you, we had 3 cocktails and a coke at the resort last week = $64.
A three course meal in a table service with a bottle of wine = $200
three counter service meals = $48
a cheap pin = $9
A night in June at the HNY = $550
So be prepared.
To answer your question about cash booking windows, they open up about 6 months in advance, so June bookings can often be made by Jan/Feb.
Europe is not as tolerant of people changing their minds, so booking requires a 10% non returnable deposit, after 3 months before your journey, you are liable for 50% and 30 days out 100%. Also you have to pay a fee for any changes, and once booked cannot opt for a cheaper option. This is not just a DLP thing, but is pretty standard.
But all of it is totally worth it. For pics and stuff to whet your appetite, you may wish to check out my trip report from last week.