"You" is indeed better but the reason is psychology, not language. "You can unlock" makes the customer feel more powerful. Wow! I can unlock something! I must be special.

I prefer it will unlock, as it’s the system that unlocks the perks for you

Either can be right, it depends on if you want the emphasis to be on the "you" doing the action of unlocking, or "it" (the system) doing the unlocking ☺️

Because you used "you" in the first clause, it is more natural and more proper to also use "you" in the second clause.

Becoming a member unlocks many perks including more videos like this one. When you become a member, you will have access to many perks including more videos like this one. Native speakers would say the other constructions, but they sound a bit ugly and imprecise.