Say a chunk goes from 736 to 752. If I make a 16 by 16 plot does it have to be exactly the borders of that chunk or can it be, say 740 to 756?

It has to be on the chunk grid system, which when you do f3 you can see it on your values there at what part of the chunk you're in.



See the "(2)" and the "(4)" for the x and z at the end there? That's the position in the chunk you're in. It goes from 0 to 15. A chunk is the same thing as a plot, so they can only be on the grid systems like this.