I would like to get some advice on hanging a framed painting (less than 50 lbs)
on a granite wall. Slabs appear to be 1-3/4in. thick and rough surfaced).

The piece now hangs on a drywall wall with triple hanging hooks with D-rings and wire loops and a security (T-screw) screw on the bottom.

My experience is limited to masonry when it comes to harder surfaces.

I imagined drilling a hole pointing down slightly with a diamond tipped bit appropriate for the substrate for each hole (3).
using plastic anchors in the holes and hanging the piece straight on the screws from the wire loops with a washer on the screw for safety.
same idea for the security T-screw on the bottom: hole, plastic anchor T-screw

Any advice would be greatly appreciated.