Can we get direction how and when we should update our SCCM PXE non-wds environment during this process?       
Step 1 – Firmware Readiness Inventory and keep all the devices up to date OEM Firmware
Step 2 - SCCM ADK Upgrade to latest version and Dual Boot Image Configuration so we can support legacy and devices that are updated in progress

Step 3 - Enable Secure Boot Certificate Deployment GPO