Apple Smart Keyboard

Hi Holger. You can simply press Control + Option + K to start keyboard help.
Then, any key you press, VoiceOver will speak what it is. You can also press Key combinations and VoiceOver will tell you what action that combination performs.
HTH,
Dave

The lay-out of the smart keyboard is a bit different than other keyboards. . First, the up and down arrow keys are merged. Second, there is no escape key. Third, there are no F keys to control specific functions such as screen brightness and such on the fly. The absence of these keys impact VoiceOver users in a few ways. As the escape key functions as both an escape key and a back key, a new keyboard combination has been developed to still allow this functionality. This is VO modifier plus the accent key. VVO modifier either consists of control and option being pressed together, and/or the caps lock key being pressed along with whatever key the command calls for. This is dependent on your settings for the VO modifier keys.
The merging of the up and down arrow keys, as mentioned above, also impacts VoiceOver users who wish to use Quicknav functionality. Because of this merging of keys, the user can no longer press the up and down arrow keys together. To address this issue, Apple has made it so that you must press up, left, and right arrow keys together to perform the equivalent command to double tapping, which has conventionally been pressing the up and down arrow keys together. You can always press the VO modifier key with space to achieve the same result. All other Quicknav commands are not effected.
It's not a full on description, but comes from notes I took while looking at one. The bottom row will have, control, function, option, and command. TO the right of the space bar, I believe, are Option followed by Command. Though I could be reversing the keys on the right side of the spacebar. I wasn't a huge fan of it, but I hope it works for you. Good luck!

Scott, I think you have the bottom row slightly wrong. I have the Magic keyboard for iPad Air and apple’s external Bluetooth keyboard, both of which from left to right go: FM, Control, Option, Command.
Holger, The Option key effectively replaces the Alt key, yes. However, there are various differences for this set of keys on Mac versus Windows. The keys are placed in a different order, and where windows has a Windows key and an Alt key, Mac has a Command key and an Option key. They are used differently sometimes too, for example copy on Windows is Control + C, whereas on Mac it’s Command + C.

Dave: that one was actually a typo, but I'm glad you caught it. I'm guessing, then, that the latest model still does not have function keys, an Escape key or a sepearate up and down arrow.
If you are unable to launch VO help, you can also perform a 4 finger double tap on the touchscreen to launc This. Perform a 2 finger scrub to exit, or VO with grave accent to hit the escape key.

You’re welcome Holger!
I am aware you were talking about the iPad with the keyboard. The keyboard I have is the magic keyboard which attaches to my iPad Air model, but the one you’re getting is very similar.
And the keyboard help mode is software, available on all iPads, and will literally tell you what every key is on the keyboard. And in reality, it’s extremely similar to any windows keyboard you have used, just a few differences as we’ve outlined above. So I’m not entirely sure of what you want a guide for beyond that, but given the huge number of different keyboards out there I don’t think it’s hugely surprising that there isn’t a detailed written guide for each one.
Enjoy your iPad.

The keyboard I described is the Smart Foleo case. I verified today while at the Apple store for a project I'm working on that the lay-out is still the same.
As you know, AppleVis is a community-driven website. Since you will be getting this keyboard, and then your iPad next month, I hope you will consider writing what you were after so that those looking for this information in the future can find it.