We stayed near Windsor Hills Dec 2016 leaving on December 23. We did not think the roads (I92) were that busy, except for I-4 which is common. Tip: check google maps for traffic before you start driving. There are many options for getting around and we frequently changed our route based on current traffic conditions.
We had no problem getting into restaurants offsite either.
The parking lots at Disney Springs both filled by about 2pm or so (all 4000+ spaces). It might not be possible to park there if you arrive in the evening. Disney Springs was a zoo. We thought it lost a lot of its charm since it was being crushed by so many people (and we were there during the day - I can't imagine what the evenings were like). There was a 240-260 minute wait for kids to see santa during the day. The staff was giving out pagers and telling people to come back in 4 hours. Unbelievable. The deluxe resorts had character interactions with much shorter wait times (10 minutes or so). Parents were very grateful for that option.
We did the Christmas shows at Seaworld and really loved them. We spent some time at the Disney hotels to see the Christmas decorations and listened to a lot of people complaining about the crowds in the parks. Christmastime is so magical that most people said it was worth it, but we were thankful we chose to see Busch Gardens, Seaworld and Aquatica instead. It was 82 degrees in late December when we went to Aquatica. I could not believe it!
I think the month of December is the best time to see the parks and resorts. Just make sure to pack your patience.