Ray,
This is a very good question and there is some good news and some less good news. First, the less good news.
Lamination PRO is stricly a 2D design tool. It has no concept of depth and so there isn't any way that the program can help you with the thichness issue. However, since you intend to make a feature ring for Woodturner PRO, I would first make your desing in Lamination PRO and then create a single ring in Woodturner PRO at the correct size for the design and with the desired number of segments and a sample board width of 3/4" (for example). Then click the Ring View of that ring and you'll get an idea of the wall width that will be available after a minimum turning to get the inside and outside diameter round. What you cannot do, though, is to visualize what the pattern will look like on the inside diameter and this is a critical part of the design.
One of the things you need to consider with the SW design is the space at each end of the segment that will not be part of the pattern. The more you increase the width of the center kerf, the more the design will move towards the center and this is important if you want the complete design to be visible from the inside of the vessel.
Another way to accomplish this is to glue a small vertical spacer to each end of SW segments. This is more work, but the effect can be great, especially if you also add a thin segmented row to the top and bottom that will basically frame the design and allow it to be completely visible from the outside as well as the inside. The other consideration is that the fewer segments you have in a ring, the longer those segments will be and the curvature becomes greater which affects the design. So within reason, the more segments the better in a feature ring like this. Also, the ring needs to be a a place in the vessel where it is nearly completely vertical.
With regards to the length of the lineal laminate, the calculation simply shows you the minimum lineal lenght of a design that can be cut to make the desired next generation. If it shows 48, though, would not start with a 48" board as that becomes difficult to manage and hard to keep straight. Instead, I would make two 30" boards or better yet, three 24'" boards and start with those. Yes, there is waste, but when you get to the end, the waste of one board can be glued to the start of the next board and you shouldn't lose much, if any.
I hope that helps, but please let me know if you have additional questions.
Lloyd