No, effective edge does not control how easy it is to spin. Effective edge is the length of the board that is directly in contact with the snow. Total length of the board affects the swing weight a little though. So look for a slightly short board - (140 - 145) cm. Shorter boards tend to be softer and easier to flex. How about the  Rome Detail 143 , that company ships internationally AND accepted returns AFTER you ride it. 

However, based on what I've read of your posts I believe even the best snowboard is not going to let you do 360, 540s at this point in time; buying a really expensive pair of basketball shoes doesn't mean you can suddenly do a slam dunk. You need have the proper strength and training to do that trick. Once you have that... it doesn't matter what snowboard you are riding.

Similarly, you need a fairly flexible board to do flat land tricks... but again, my guess if that you haven't been taught the correct way how to do it.