1. Yes you can import image overlay from KMZ (not KML since it could not carry the image file it refers to), and this function is a free function of the app, so you don't need to pay anything for using it.
Imported overlay is called as "Image Overlay", which could be listed and managed both in the User Data and the Custom Maps list.
NOTICE: Rotation and scale is supported, BUT
Quad is not supported, which means the image overlay should be common without "Convert to LatLonQuad" in Google Earth.
2. The app also support import image overlay directly from files, iOS photo album, iCloud Drive, etc.
Images imported works just the same as imported from KMZ, so using KMZ is much more preferred, since it could adjust boundaries and rotations much more easier while doing with a desktop computer than a small screen phone.
More details here:
http://duweis.com/support/viewdoc.html? ... ageoverlayMore tips: while working with huge image, for example, larger than 50 MB sized, it is suggested to convert the image into tiled format such as MBTiles, which provides much better loading and refreshing performance, here is a article about convert geotiff to mbtiles:
http://duweis.com/support/viewdoc.html? ... bt&from=mpBtw, the app always get a 7-day free trail after installed or reinstalled, in that week, all functions are fully free and you can try everything it could do before decide to pay any enhancement.