I just measured my boards like this and for an 8", I would use and 18-19". Hope that helps.
AI'm not sure if it's black buttercream / ri or fondant. Using my phone and can't zoom in enough. But I guess it's fondant. Measure your cake pan to find out the length. I use a simple pizza cutter, you'll get in any supermarket. For the logo I'd say - if you cake is 4" high - 3" high and 5" wide.
AOh, and the CC logo I guess is 2,5" or 3". If you use an 8" cake, the top layer would be a 4", right? Means you have about 4" left in front,but you need some space to the top layer and bottom cake border. Use round cutters or if you don't have them, maybe 2 glasses in the right size.
Could it be extruded fondant for the border?