It can be pretty confusing...here's my attempt at making it a bit simpler:
If all your contracts are titled exactly the same way and are the same UY, then they will be treated as one master contract with the other ones being "add-on's"...so, if your master contract is number xxxxxxxx, add'l contracts will be xxxxxxxx.1, xxxxxxxx.2 (etc.). You'll be able to combine points at will so long as they're at the same resort. If they're at different resorts, then you'll still be able to combine points at will at 7 months out, but from 11 months out to 7 months out, you can only reserve with points at your home resort for reservations at your home resort.
For example, say you have 3 100-point contracts--all titled exactly the same and all w/the same UY...in the first example, they're all SSR contracts. In the second, two are at SSR; and one is at AKV...
At 7 months (and closer), you can use all 300 points on any one reservation...
Between 11 months and 7 months from the start of your vacation, you can only reserve at SSR (in the first example); in the second example, you can reserve a villa for up to 200 points (or 400 or 600, w/banking and borrowing) at SSR, and for up to 100 points (or 200 or 300, w/banking and borrowing) at AKV...
If your contracts are titled differently (e.g., on one you're the sole owner; on the other you own w/your spouse), then they are separate master contracts...you can link reservations made w/each contract, but can't combine the points--this could get tricky if you have enough points in both contracts for one night, but not enough in either contract (e.g., say you need 24 points for one night; you have 12 left in each of your two contracts...you can't combine those two 12-point contract amounts into one 24-point reservation (whereas you could if it were one master w/add-on's)...
If/when you go to sell, each contract is sellable separately, whether it's a master w/add-on's, or several separate masters...
Does that help?