There's no recording of this lab. However, we do have an IoT MVA which covers the same material.
On-board LED on Pi3. We didn't use it for the lab. I know it's not accessible the old way, but I haven't checked on any update.
The WiFi driver for the on-board WiFi was not yet ready for Build, so we used WiFi dongles like you would on the Pi 2. It's coming, though.
Windows 10 IoT Core on the Pi does not have GPU accelerated video. The Pi has a very different type of video system that doesn't meet the required DirectX feature level. If you want HW accelerated video, I recommend using the Dragonboard or another IoT Core compatible board.