That depends on hardware independend your image is...
You need to copy drivers after the image is restored, but still in WinPE, before the device restarts and boots into Sysprep's mini-setup. That's the phase when Windows loads and installs drivers.
So I would include the copying of the drivers before the sysprep file was injected under Post-OS Installation or would I add copying of the drivers after the deploy image action in OS Installation?
Either way, so long as they are there before it boots into the OS the first time. Also, make sure you have your sysprep written to take advantage of the drivers. As far as the number of images, you can have a single image with some work. Many people find it easier to have 1 image per HAL. I create my templates according to model number, each one housing the hardware specific details required. I copy it and add the apps required to the copied template and fire it off.
I personally prefer to do a scripted install rather than a syspreped image. Take a look at the following doc:
What you can do is use a %model% variable that queries that inventory item, and that way it can be hardware independent.
This alleviates some tough problems inside sysprep. Otherwise most of the steps are the same including copying down the drivers.
Relating to your last question, it doesn't matter if you copy the sysprep file down or the drivers first. you just have to do both before the reboot.
I've clicked onto this document link you gave me. It's returning an unavailable page.