Q1 Batch file: This is an independent batch file from MDT. We do a few clean up actions just before sysprep and power off. We do this via a batch file and at the end of the batch file it runs the sysprep command with a consistent syntax. That way we get the same exact action every time we build a master image and then sysprep it. It could be done manually by copy and paste, but its much easier to run the batch file. We do have the sysprepit.cmd file as well as some branding stuff installed as a MDT package. That is how it gets copied over to the reference image as a MDT package.
Q2 CAB file: Understand there are 2 different cab files in play here. We install the winpe cab file in the reference image since that contains the core drivers we need post deployment. The driver path /images/drivers/{hardware_type}/{os_type}/{arch}/{driver files} is the extract of the model specific cab file. If you give me a specific dell model I can point you to the proper cab file.