If I Buy with Streak will the margin be considered? If yes then is it the same as the broker or different?
Your stock broker provides leverage for your trades. Streak does not provide any additional leverage.
Streak does not consider margin while backtesting or deployments. However, when you deploy a strategy and take a position, your broker blocks the margin required for the position. So there is no additional margin required when you enter a position with Streak. You need to keep just enough margin as required by your broker to enter a trade.