This is information on optimizing, updating and locking the Q.
They are all different things.
Optimize means changing your shipments to get as close to the budget as possible.Optimizing will change your shipments to fit the most for your budget according to how your Q is set up. Meaning if you are a consultant and have "updated" your Q to go over budget, optimizing should change your product according to the subtotal so it won't include tax and shipping. If you have not "updated" your Q or you are a regular customer set to go under budget, optimizing should change your product including tax and shipping to fit your budget.
Updating is an option for consultants. A Q that has not been updated will include tax and shipping into the budget where an updated Q will just look at the subtotal.
Lock shipment does mean that the program won't change anything to a Q shipment. There is an exception with price changes. If price changes brings you too far over your budget it can drop out an item so you won't go over. This is determined by how far over your budget the price change takes you and whether your budget is set to o over. The owner of the Q can go in and make changes as well even when the shipment is locked.