Dan
I often use the term inlay as I think that is a more generic term that fits them all. Though I have also heard it used only for times when the pattern was cut and the metal was either glued or hammered into the pattern
I have always been told that in niello the pattern was cut out an then filled with a mixture various of silver and lead alloys. this makes the fill black against the metal color
In koftgari lines are etched into the surface then the metal is pressed onto the scratched marks in the shapes needed then it is heated to help it adhere
All I could find on chasing describes it as an "embossing" on metal
Repousse the metal is hammered into the pattern
That being said I am not as cautious to use these terms properly as I should be. This my understanding of the terms only and I look forward to comments from those more versed in this than I am
John