Hey Riot. Thanks a lot. I'm glad you liked it.

I'm so happy to be here. Putting music and video together makes me feel complete.
I'll try to answer your question. For starters lets give credit where credit is clearly due - you can thank Eric Persing and Apple for much of the sound. They are the real sound gurus here.
I know you already know all this Riot but here is what I did which contributed a little to the sound. The goal was to make this a 6 minute full featured video. What I wanted was a movie theatre sound. Not all of my movies will have that but this one called for it.
I started out with a few Apple loops for some of the fx. I noticed that they were in surround sound and had that wide sound. So I knew I wanted to match that. The patches I chose then in Omnisphere mostly matched that. But some of the Omni sounds weren't quite there and I saw that they were in stereo so I changed them to surround sound and also added reverb to taste. Changing them to surround sound and adding reverb had a 'blurring' effect on the sound so I had to be careful to get exactly what I was looking for. The sound effect on the flare on the Rendezvous title is an example of that.
For all but the middle electronica part, I tried to use one sound at a time or combined a couple of sounds to make the one sound. I focused on getting the right sound without cluttering up the space. So there was nothing to drown out for the most part. But if you do have a wide sound then the second sound must cut through and/or has to be located in a different part of the 3D space. One big sound can take up a lot of space in the field!
The key is defining your sounds in a 3D space. For example, in the opening theme, there are 2 sounds - these are the same at the end. Both are close in sound but the horn is a little higher and a little louder. On the electronica part, there are 4 patches that basically make a combi. You can hear that the arp is the closest to you. I put a touch of reverb on it so it wouldn't sound totally dry. One of the patches had a nice little spacey thing on it so I chose that to add space to the over all combi. Had I put much more reverb on the arp it might have sounded muddy and the clarity and separation would have disappeared. I wanted the electronica part to be closer over all to you than the rest of the movie but it still has an element of the wide space sound and that one little space sound is lower in volume and farther back in the space.
So when you're working in 3D space, you consider top to bottom, left to right, and back to front. If you add all the sounds in one spot in the space then you don't get separation. You get mud. Reverb, volume, pan, and the tonal quality/timbre/frequency of each sound helps define the space. Other things do too but these are the most obvious. So mixing is important to make sure all these things are placed in the space where you want them. I took lots of breaks in between sessions so I could hear with fresh ears every time. That's really important. I also work in headphones so I can hear every detail crystal clear.
All that said, I don't really calculate much of this. I just know what I want to hear and I play until I get it.
When I bounced the track I bounced it in surround sound and then tried it in stereo. I didn't lose any of the space in stereo and the file size was much smaller. I also knew that most people wouldn't be listening on surround speakers so I went with stereo.
And finally, after all that work, about a month or two, I chose not to compromise on the video or sound quality. The audio is 48KHz and 360BR. Why go to all that trouble just to squash out the frequencies in the end.