WRT the time/quality, I simply meant to say that in general, the more compression the worse the quality. Though small file sizes can also be made with lower data rate which is also lower quality, but can be done quickly.
Converting original multi-track audio to aac is a waste of time and only ensures that it has to be decoded and sent as PCM by the player. It also means a complete loss of multi-channel surround unless your audio pre/pro/receiver can handle 7 channel PCM over HDMI. It means you can't use an optical connection for surround. Always leave the audio as AC3 or DTS if available. If it's FLAC, go ahead and convert it, but better to convert it to AC3 using something like Popcorn Audioconverter.
The tradeoffs associated with 10bit encodes are significant enough that the process is largely a waste of time (ie. Don't do it). There's no way to know at this time if 10bit decode of H.264 will ever show up in consumer hardware and if it does, whether or not it will be compatible with the existing encoded content. The bottom line is that it's only suitable for playback on a computer with a limited set of playback tools.