The images currently available do not have a password set, so you must use cloud-init to configure one. We don’t expect this to change as it’s how cloud instances behave in general.
What will change eventually is that we’ll get the agent started automatically which would then allow you to use lxc exec similar to containers and not necessarily need to set a password. Our own images (images:xyz) will all have the agent units in place to do that and we will be pushing the same through Ubuntu, but if using something else, you’ll be on your own.
As for GUI access, right now, it’s not something we’re doing. We will most likely introduce a raw.qemu which will allow you to pass additional configuration, including the VNC address. That should work as a stopgap measure for those who absolutely need graphical access (such as installing Windows).
The long term plan is to setup a virtio graphics card and connect it to a spice channel, forwarding that spice channel over websocket through our normal console API. Spice clients are reasonably widely available and could then attach to the VM’s graphical console, keyboard, mouse and possibly even USB.