Mango trees will survive and produce without external input here, but peak production and quality is obtained with good cultivation practices, including irrigation in times of drought, fertilization (generally without nitrogen), pruning, and fungicide treatment.
Tree trimmer's mulch is great, but over time it will lead to Ca and micronutrient deficiencies (I've written about this topic on several other threads). So, you really want to use it in conjunction with a fertilization regimen.
0-0-50 is great if all your soil lacks is K. Generally, it's trickier than that though. Too much K, for example, can lead to a deficiency of Mg (and Ca I believe). Iron, zinc, manganese and several other micronutrients tend to be in short supply here.
And if you have trees other than mangoes, many of those do want nitrogen.
The products showcased in the video are all excellent.