But I think most keyboards (for Mac, for Windows) also allow us to adjust the volume and brightness. So, having an Android keyboard does not make a difference except activating email, calendar, web browser? As the tablet will be placed in a very close distance, one could also use the touch screen to activate them. Can I assign special functions to some keys of non-Android keyboard such as the Logitech Bluetooth Illuminated Keyboard K810? That could be very useful.
Not the same. With the hotkeys no matter what you're doing or what app you're using you can open internet, mail, or calendar in ONE button press. Without the hotkeys you need to switch out of your app, swipe to the icon, and hit it. That's three presses minimum. It doesn't sound like a big difference but it is and you'll get used to using them (and annoyed without them) quickly.