Quick Sync is hardware video encoding and decoding technology that's comparable in speed, compression ratio and quality to x264. Since Quick Sync is a dedicated hardware core on the processor die, it allows for faster and more power efficient video processing.
You can download a plugin called DirectShow Audio Source, but you're only given options to use audio inputs (mic, speakers, etc...). You cannot simply select a wav or mp3 file to loop (going AFK or BRB for example).
Wirecast offers an option to create and automate playlists - even with live shots - by modifying the duration of each shot. Playlists also can be used to create highlight reels after capturing Instant Replays.