[...]For printing, I get better results in Qimage...whether you agree or not.
But I do need to do print sharpening some place and it is easiest to do on export from LR.
Although Jeff did answer your question about display ('screen') sharpening, indeed display pixels are display pixels (although a matte display might need a bit more sharpening, I'm also not sure on which basis the built-in solutions were founded), I also do agree that for high quality output there is more than LR alone.
Whether you agree with the way I want to do it or not, please answer my question about how the sharpening works. I agree to understand your warning and be fully responsible for the mistakes you tell me I am going to make.
Since display pixels are relatively low resolution, one cannot sharpen display pixels too much without introducing visible artifacts, such as halo. So in that sense, it's what-you-see-is-what-you'll-get, which is more or less what Jeff said.
However, there is indeed more to that story ..., there are different ways to tweak those pixels into suggesting higher resolution, without artifacts showing too obviously. Look at the attached examples which are pretty well downsampled with ImageMagick without, and with 100, 200, and 300% deconvolution sharpening, added.
Given your reference to Qimage, it may also be useful to look at some prior threads (here
) on the general subject.