There is a bug in iOS12 when sharing drawings with white color. The white is outlined incorrectly. In addition, the highlighter pens are not rendered correctly. Apple has acknowledged the problem and no solution is available at the moment.
------In general iOS12 has been a great beta. I haven't noticed anything major at all and it seems faster. I am still testing the release version but so far everything looks great!
WiFi and even Auto Connect worked for me.