The Disneyland boxed set will be 6 CD, yes. The version sold at Disneyland will come packed with a bonus vinyl recreation of the Walt Disney Takes You To Disneyland, yes.
The 2 CD set will be a separate release which will be a condensed version of the box set. In other words, the ride-thru's will be shorter. Basically for the not-so-hardcore fans that don't want to spend $$$ on the big box set. If you buy the box set, you probably wouldn't need to buy the 2 CD set.
The single CD version is just for the tourists that just want a simple souvenir. It will just be highlights.
In other words, you won't have to buy all 3 sets to get all the material. You have the option to buy as much or as little as you want. If you want all the audio, just buy the 6 CD set. If you want 2 CDs worth of material only, get the 2 CD set. Same with the 1 CD set. The 2 and 1 CD sets will most likely include material already on the 6 CD set. Choices, choices....
I assume if you are in a Disney music chat room, you are enthusiastic enough to want the 6 CD set.
Assuming all goes as planned, if you buy the 6 CD set, you won't need to buy the 2 or 1 CD set. (unless you are a hardcore fan and also want shorter edits of the complete soundtracks offered on the 6 CD set.
Simple?
Your friend,
Louis