Does this wall look sound

I don't believe the thickness of the cleat is as critical as the type of wall anchor being used. The cleat holds the cabinet in place, but it's the anchors which are really bearing the weight. I would make my decision based on the type of wall material holding the cabinet and use an anchor rated for the expected weight of the cabinet for that particular wall material. If you have a regular drywall and wooden stud construction, I would probably use the screws used to hang kitchen cabinets as they are designed to carry a pretty heavy load. You could have a 1.5 inch cleat with an inadequate anchor and the cabinets will pull it right out of the wall.

My guess is that it's either a sandwich beam (wood sandwiching a steel plate) or simply an i-Beam. When you drill, are you drilling through wood or just sheetrock?

If it's an actual i-Beam, you could hang it with some sort of clamping device.

I wouldn't trust dry-wall anchors for hanging a punching bag. Dry wall anchors can hold quite a bit, but not the active load of a swinging punching bag.