ok, here are some, and yes, layout is flexible, but i only added 'hide' button because it's fine for me
as for documentation, probably looking at example layout files. they're in the source package, i have put some of them in the same place as binary, for example german layout:

mkdir /etc/X11/app-defaults/
wget -O/etc/X11/app-defaults/XVkbd-german http://mrrau.dyndns.org:23280/n800/x...Vkbd-german.ad

then you will have it selectable as a runtime menu option