The backtester is a tool to find the best strategies, settings, parameter filter options, and timeframes for a particular asset. Results will vary for each asset and timeframe and can be tuned to optimize for each. It is not meant to show you how much profit you will make as markets will vary, rather to help adjust settings to optimize the strategy. Each person may have different strategies and results from their own strategy and preferences.
You can use the backtester to find which TP and SL worked best for that particular asset and timeframe. In some cases adding a SL or TP may improve results and you can adjust them to find the optimal TP and SL, and in some cases it may not and you can not add those parameter options.
By default the LONG/SHORT strategy is set at the +TR and -TR trend reversals which is an aggressive entry which can catch trend reversals before they occur. This can give great entries before a trend starts at the reversal, however, is more aggressive because it is against the current trend still. You can add more filters from the parameter options to adjust the LONG/SHORT strategy to your preference. Additionally, you can add your own custom TP/SL from all the custom options and trailing stoploss options.
Backtester can be found here: https://www.tradingview.com/script/kQfGOYuK-Kashikoi-BACKTEST/