Many people use Plex, Emby, Kodi etc to play their movies. These players are able to convert for example a DTS track while playing the movie to AAC or AC3 if the client does not support DTS. Many people add an AAC track to avoid this transcoding. Of course this is a good idea, but instead you should add AC3. Reasons:
1.) Many movies already contain an AC3 track and do not need additional tracks at all
2.) Sonos does not support AAC
3.) Roku does not support AAC
4.) Chromecast does not support AAC (anymore)
And finally I do not use MakeMKVs audio conversion at all as it slows down the ripping process. Instead I use Popcorn Audio Converter to automatically add missing AC3 tracks to multiple movies in a parallel process. Of course its not perfect (for example 7.1 audio), but finally its much faster and AC3 produces less problems.