Different candle intervals have different backtest window. The backtest window for various timeframes is listed at : Create (Basic) - Streak Help
For 15 min timeframe, the maximum backtest window is 3 months, and for 1day timeframe its 5 years. However, this window can be shifted to older dates by changing the start and stop date under the ‘backtest parameters’ section
Position Sizing and Max Allocation are the Risk Management tools available in the Streak Platform, you can make use of them with an active Streak Subscription.
To learn more about Risk Management in Streak, refer to the link below: