My main tines are 1/2”. The in between pieces are less. Don’t know what steel it is but probably nothing fancy. As far as impaling things, I can see that with hay bales but nothing else. I can scoop up anything. And my argument for a narrow one is it digs much better, when trying to uproot a 6” tree. Kinda like digging is easier with a spade than a snow shovel. But if you don’t dig and only scoop, a wide one is fine. But my 48” will scoop up a bigger pile than you can see around. The other problem I would have with the unconnected tines is that when I knock down a tree, the first thing I do is push it from high. Then back up, plunge under the root ball, and curl up while inching forward. Those widely spaced tines would not allow that. The tree would wedge between them and bend them. I don’t care what steel it is, for a big tractor will bend it.
As far as two thumbs, my narrower one doesn’t need it. Once I grasp it, it goes no where. Now of course a wide grapple needs two.