I have done a few projects with tree sections. I used pieces about 12" in diameter and between 1/2 and 1-1/4".
My ex-husband and his buddies liked to play with chain saws and try to see how thin and even of a cut they could make, I got first pick of the pile. It works best if the tree is long dead and dry before you cut the tree cookies, less warping and cracking once they are cut. When cutting a cookie from a fresh tree you will get all sorts of cool warps and cracks. One piece ended up warping into a bowl, it looked really cool. Some pieces have small cracks that the epoxy method works great with (I used one of the self mixing syringes of clear epoxy). Some pieces end up with really big cracks, but can be incorporated into the finished project. Some pieces are just fire wood. I would guess that 30% of the big cookies were useable when we cut them. I could have probably had a better return if I had a thickness sander to make an even piece.
I also cut quite a few ornament and jewelry pieces from branch sections. The little ones warp a lot as they dry, and some species are less prone to cracking.