2 questions about DS716+: Problems with mkv/DTS-files AND support for hardware transcoding?

Hi - as topic says, a couple of questions :)

1. I have PLex running on my DS716+ but I am unable to stream mkv files with DTS sound to Chromecast without any stuttering. Works fine if the sound is AC3, so I guess it's putting too much load on the server. Any suggestions to improve the stream other than remuxing the file?

2. Any chance that hardware transcoding will be supported by Plex on the DS716+?