Welcome!
This
post should answer most of your questions.
As far as the resorts which offer it, it's only available at deluxe resorts.
The GF has two levels, Lodge and Royal Palm Club, with RPC being in the main building. It offers a higher level of service and amenities.
The Contemporary also has dual levels of concierge. On the 12'th floor they offer "concierge light" with reduced services and amenities. The 14th floor offers full concierge services.
The WL offers concierge light only.
The BC, BWI, YC, AKL, and Polynesian offer full concierge service and amenities.
Each resort, and each concierge differs in decor and amenities. There are many threads on these boards about concierge and what guests enjoyed and disliked about the various services.
Anne