I'd recommend a tooth bar with large longer teeth in it as posted in the pic earlier. I got one similar (construction attachments brand) and it works great. I always back drag with the inside curve of my bucket with the teeth raised. If you lower the teeth, it's going to leave marks with some people don't like (though they are IMO not back dragging correctly).
This is the style all larger equipment has for a reason. Those teeth essentially reduce the surface area that digs in, which multiplies your digging force up till all parts of the bucket make contact, so it's important to have longer teeth because the increased digging force is only the first X inches. With the teeth, it's no problem for me to dig in with my 66 inch bucket into anything other than sand rock. You can use the teeth to break up the ground, tare up roots, remove rocks, and etc. They're made of some high grade steel and hold up and also reinforces the bottom bucket edge.
I'd avoid the 'beveled edge' bars as those are nothing but combination tooth bar + cutting edge. When they dull, they're not as effective at either. The design of these is to cut brush, but IMO there's better tools for that and you're best off doing that kind of work with a grapple. Put a tooth bar to enhance the bucket's ability to do what it's designed for...dig in and move material.