What ever you try, try it out on the back yard steps first.
All I've ever seen is new construction that I suspect is a lesser psi concrete as there is less of it because weight is not a concern. They simply drill a hole big enough for the "leg", usually close to 1" square, drop in the rail and grout it with anchoring cement.
You may not have the material available with precast for a hole this big close to the edge for this method.
I'm sure someone familiar with precast will chime in. I'm just thinking that with a tapcon that the natural sideways pressure that will be exerted will subject almost a crowbar effect on these and once the holes or fasteners are "shot" ....
3/4 steps also could attach to a wood post at the bottom and the building if there's no landing at the door.