After receiving the 12-60mm lens, I did some testing and determined that it was on par with the 14-140mm as far as sharpness in concerned. So I headed off to Europe with the 12-60mm in my bag instead of the venerable 14-140mm. I did appreciate the extra 9 degees field of view that the 12mm afforded but, at the same time, I occasionally missed the reach of the 14-140mm. But the results of my shooting with the 12-60mm were somewhat disappointing. Though my preliminary testing showed both lenses to be similar in sharpness, I (subjectively) didn't like the images taken with the 12-60mm - maybe not enough contrast, I'm not sure. But the biggest problem was with lens flare whenever the sun was not at my back. Many an image was degraded when the lens was even slightly pointed toward the sun. This issue was relatively insignificant when using the 14-140mm.
Bottom line: the 14-140mm is back in my travel bag.
Here is a slideshow from the trip that included Belgium, Netherlands, Germany, France, and Switzerland. Some of the images were captured by my wife on her phone camera and most of the rest were taken using the 12-60mm lens on my Lumix GX8. The worst of the flare images were culled before creating the slideshow.