You will find, as a common rule of thumb, that a good mix can reduce the amount of work needed to do in the master at mastering time. Generally, mixing work is more intuitive, but also a lot more involved than the mastering process, and the mastering process cannot fix mixing problems. Clearly, a good mix is needed no matter the situation.
You are asking how to get a crisp, clear, cinematic sound, and this is mostly done through the mixing. Let's suppose you grab your nearest string library, and put down a few staccato chords, just like in the example you gave:
Out of the box, you will have exactly what you'd expect: A couple staccato string chords playing without any processing. Sounds ok, but it does not sound professional by any means.
If you try adding some normal reverb plugins, or try doing post processing without good knowledge of how it will effect he mix, it will go from sounding like "not professional" to "non professional with effects yay"
Here are some things I keep in mind when mixing to achieve the sound that you desire. This is not one size fits all, and it will require you to know how your edits will affect the mix
- The first thing I do is set up parallel reverb. I will send the sound from my orchestral plugin to two different mixing tracks, one track will be for the wet reverb, and the other track will be the dry signal with minimal reverb. As a note, each instrument can have their own dry track, but they should all share the same wet track so they sound like they are in the same room.
This is done so I can process the reverb and the raw sound different from each other. This is especially important for orchestral settings, as the reverb from the orchestra will be surrounding the listener (think a theater), but the raw sound from the orchestra will only exist at where the musicians are sitting.
This one is pretty simple, try to imagine an orchestra (or look up a seating chart) and set up the stereo imaging and/or panning of each instrument to match their seating position relative to the audience. Instruments with lots of overtones will be more stereo spread than ones that don't. etc.
On the dry track for each instrument (from the parallel processing) try to EQ each instrument to fit their desired frequency range. The simple idea is to make the low, mid, and high frequency instruments only exist in those ranges, but also allow each instrument to produce their desired overtones. However, as I said in the previous example, I tend to keep the overtones in the wet reverb track.
Don't make your mix too loud. Digital orchestras are fragile to being compressed and distorted when they get too loud. Your sound will be much more clear at a lower volume, and you can always bring up the master if you must at the end of your mixing process.
If your original audio is bad, then no mixing process can make it sound real and cinematic. You will need a good recording to achieve a good result as you desire.
The above points should be used as guidelines, not solutions. This really depends on how you want to sound, and decades of study and practice can go into this topic. You are doing good by following tutorials. If I were to be blunt with you, once you have your mixing fundamentals and concepts A-OK in your head, you should be able to deduce how to mix and produce your desired sound on your own.
ALSO as a note: Convolution reverb will probably give you better results than digital reverb, as the reverb is created from a real life sample. I use samples from real sound stages to create a reverb based off of a real room.
Hopefully this answer can give you some insight, as I have described just a small portion of what goes into creating a sound like that.
