I'd think best to use a greyscale image. PS does that. DOgwaffle and others too. Then you can essentially start by typing thetext with text tools, white on balck. White is high raised elevation, black is low. Various grey levels inbetween by way of blurring or smoothing the greyscale elevation map. Want to add old weathered look for a dino tag? add erosion, noise,...

The load the greyscale and turn it into 3D. Add thickness. to make it a solid. Most 3D printers need it as a solid.

If you're on Windows 10 you have an app included that can take your greyscale and add thickness to it. I'd think PS can do it too. Then export to STL or OBJ and use the 3D app on Windows 10 to load and print. The app is called 3D Builder, included with WIndows 10. The Creator's edition has painting options too if you want to colorize deep places for a rusty look for example, when it's a metallic plaque, or other aging effects for cardboard texture, wood etc...