I like where this product is headed, but it still needs some polishing. The units have stats similar to creatures, but the author went with an unified attack and defense mechanic; attack is basically attack bonuses + medium damage that is rolled against the unit's defense (a similar mixture of AC and HP), causing damage (to the Defense) equal to the difference between the attack roll and the defense score. That means a death spiral, each attack that hits lowers the unit's defense, making it easier for them to be hit, and making it so each consecutive hit causes even more damage. I understand the idea behind this and it actually makes sense, but I think this level of detail is wasted on a system that strives for simplicity such as 5e.
Besides whenever I look at a homebrew subsystem I always think it's more elegant to use the systems and linguo already present in the rules instead of creating new ones. The units could have attack and damage, AC and HP just like other 5e creatures. One could represent the death spiral mechanic by giving attacking units advantage on the attack roll against units with half HP. And so on...
What I really like are the rules for Solo creatures and Leaders. Solos are big monsters, legendary creatures or badass characters that can take a unit by themselves. They can also lead a unit and grant it special abilities. Kinda like many strategy and turn based games. That said I wish the rules for leaders were more developed. There are some rules for characters granting a unit special abilities based on his own abilities, but there are very few of those, with the rest being generic ones (i.e. "every fighter grants X"). I hope the author greatly expand this concept on the feature, because I believe this could be this product's main drawn.
As a nitpick there are some pieces of text that are still in spanish. Nothing glaring tho.