I built this plugin to fulfill this request:
Trace works like Ink Sketch and similar plugins, but unlike them the amount of artifacts is a lot lower and you can fine-tune things quite a bit. It works really really good with images that are solid colors (or close), for example logos, children's book covers, anything material design. With more complex images you get more artifacts, although there tend to be less of those than normal.
In any case, let's take a look at the plugin:
Distance -- included mostly for completeness. This will make the tracelines bigger because the pixels being searched are further out -- it's more of an artistic effect than something practical.
Threshold -- determines how different a pixel and its neighbors must be in order for that pixel to turn black. Lower thresholds mean traces are more likely to happen, higher thresholds make them less likely.
Minimum Neighbors -- the plugin works by comparing each pixel to all eight of its nearest neighbors. By default, if even one of those neighbors is different, the pixel will turn black. By moving this slider up, your trace lines become thinner and you get more accurate detail because more neighbors have to be different. I recommend decreasing the threshold when you increase this slider.
Black on Alpha -- By default, the destination image is a bunch of black lines on a white background. If you click this, they'll instead be black lines on alpha, allowing you to do feathering or whatever else you want to do.
Preserve Original -- This will combine the lines with the original image, basically giving it an internal outline according to your specifications.
I'm not going to look at every setting because most of them are self-explanatory, but I will cover the more arbitrary ones.
First, a base image. I've used a collection of windows logos because they meet the "solid colors, less complex image" standard that this plugin works best with.
Here's your default settings. Not perfect by any means, but compared to other sketch plugins, it's extremely extremely smooth, bold, and you can actually adjust it to show what you want to show.
By adjusting the Minimum Neighbors and Threshold settings you can get more of the image to show. There are some artifacts, but again they're quite low compared to other plugins.
I went back to the default settings and clicked "Preserve Original Image" -- now you have the original image but it's just outlined better.