Does it matter if the dashcam is lower on the windshield or more on the drivers side in order to better read license plates?
It is all really up to personal preference... every vehicle make and model defer in design, shape, angle etc. Some windshields may have very curved glass on the sides, which will distort the image.
Try several mount positions, useing the lcd screen on the cam, or the app via wifi, to see live view and decided for yourself where you like it best.
You can also buy a pack of replacement 3M mounting squares if you want to actual mount it to the glass, vs just holding it and eyeballing things.
Typically, users prefer dash cam as center as possible, either directly under the Rear View Mirror, or, just behind it, against its mount, for a more, hidden/covert install.