My next RAW Therapee tutorial was going to be a comparison of RT's vs ACR's noise reduction routines. Unfortunate ACR was winning. Then I learned RT's noise reduction routines were having a major rewrite--see issue 1052 on the forum. So that tutorial is on hold while I wait for the new goodies to show up in an official build.
This tutorial on sharpening is short and I hope sweet.
I'm using a combination of RL Deconvolution and Microcontrast on most of my images. I can push things too hard and oversharpen but even then I don't create unsharp mask style halos. Compare the siding of the house in 200% box. Click on the screen captures and flip between the two images at the bottom of the screen for the best views.
With sharpening on and at or close to the default settings.
And sharpening off.