Help me understand

Recently along with the topic of fins I’ve noticed that the subject of vee has been more at the forefront as of late. During his gracious run as the “hot seat” host Mr. Barry Snyder would mention a specific vee on boards he’d build/built and I’ve noticed that vee has been to the fore in other recent threads as well. Being too new at both surfing and building  boards I was wondering if someone would explain when you would choose to use a flat panel vee and when you’d choose a vee with concaves, what they each do differently and what type of surf each is best suited for. 

And although I understand the concept (at least I think I do) I can’t wrap my feeble imagination around how you would shape in a vee at the fins that goes flat out the tail and have it transition smoothly.

Explanations? Tips/suggestions?

I shape the vee starting at the side fins, and then I run the planer out several inches, then another few inches with another pass of the planer, and so on. This makes the vee deepest at the fins and then it tapers into the rail line equal distance as it expands forward and back. I then put my concaves in and I do my rails last. I know some people do it different but this is what works for me, Check out the tail on these illustrations. Vee with double concaves is a combination of these.