Any sound you deliver to client, label or put into you video is your final mix. It must be the best quality you can reach with your current capabilities. You must be sure that your final mix sound good on different audio sources.
Maybe your monitors give a true flat sound (i am very doubt about this) but in real life people listen it on laptops, tablets, in cars and from different kind of low quality speakers. So you surely have to test it in a real life.
Mixing Engineers used famous “Car Test”, they goes to their cars to check the mix there. If this track works completely like they want — mix is right. But often they can do slight adjustments depending on this test.
So even if in high level studios engineers use such a tests — you must do it necessarily!
What device to use in this test? Use all that is at hand! Laptop, smartphone, tv, stereo system, headphones, car etc. All sources will be useful, after a few tests you will understand which of them gives you the best understanding of customer sound.
One great thing about this test — you can look on the mix from different sides, and you will be surprised how much issues you can find.
But be careful with adjustments, you have to do it with your monitors. The best result of this adjustments is when your mix sound good on all the sources. It can’t be perfect on all of them but the goal is to reach a gold middle.
Thanks for reading! Have a good mixes!