The pistol I have a red dot on is more for plinking. My eyesight has trouble with iron sights on many pistols and if I can see the front sight I can't see the target. The High Standard didn't need any milling as I found a grip replacement panel with a scope mount that works fine.But I know that's not an option on Glocks and a variety of other polymer frames. There is an adapter for some pistols with an under-barrel rail that goes around the slide and provides a sight base though.
I'm also a little confused on the second part, but good timing on this thread.