With a Point Transfer, the points are deducted from the sending members account and deposited in to the receiving members account. The receiving member has full control over those points once they are transferred.
When you "rent" points, you pay a member to make a reservation in your name. The other member has full control over the reservation until you physically check-in at the resort. The member that made the reservation is they only one that can make changes to the reservation, add/remove a dining plan, arrange DME, etc.
DVC will sell you One-Time-Use Vacation Points if you need more to place a reservation. You can purchase up to 24 OTU Points per use year for a cost of $15/point.