[Faster]

..... DO I have to use bootstripe paint in white or can I just use the same paint I am using for the hull? Is there a reason for using the cheap bootstripe paint like a barrier between the topside paint and the anti fouling?

No.. it's mostly an aesthetic thing, but most boats look better with the waterline definition provided by a boot stripe. I suppose that the boot stripe will absorb some of the beating the boat takes at the waterline from floating debris, but ideally you've got antifouling a couple of inches above the normal waterline to avoid slime etc from growing on the topsides/boot from wave action or a slightly listing or out of trim condition.

A nice crisp boot stripe of contrasting colour really does set things off nicely and it makes it easier to observe the boat's trim.