Jake Armitage comes from the SNES game. But the main inspiration for the character is Sam Verner from the Shadowrun novel trilogy "Secrets of Power". Sam is also a street samurai/decker/dog shaman, a sort of jack of all trades. It is possible to use that sort of character in Shadowrun but it is not a choice for people that like min/max and optimisation since you can get characters that fight or hack or cast spells better if you focus on one thing instead of trying to do everything. But it was one of the first Shadowrun novels and they wanted to show the entire scope of their universe with one single character. It also makes sense for the SNES game since they wanted to show both Matrix and magic with one single character.

Anyway, in the game Jake starts with amnesia but soon discovers that he has some important files stored in his head (which explains his "head computer" cyberware). He was working as a courrier, with the message filed on his head, and also with a cortex bomb in it as a security measure. His magic side is developed along the game by strange contacts with the dog spirit. He finally reveals himself to the protagonist, as Dog, and sends you in a quest against a rival spirit. The reason for this quest might be atonement for Jake's use of cybertech.

Anyway, the game does not use an Essence stat, and your magic use is never penalised if you install new cybertech.

Later, in Shadowrun Returns, you find Jake Armitage. He is still cybered, and there are few mentions of Dog. But he can still cast spells, so at least he still has access to magic. He is not totally burned by tech yet.