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Should I use regular or adjusted close for backtesting?
You would have to compare your backtesting to what you will be doing in real trading, and try to have the backtesting as close to your real trading as possible. Note: you may never get the backtesting to match your real trading exactly but you need to get as close as possible. The whole purpose of backtesting is to check if your trading strategies - your signals, entries and exits, and your stops - are profitable over various market conditions. As you would be using actual closes to do your real trading you should be using this to also do your backtesting. Rather than using adjusted data to get an idea of your total return from your backtesting, you can always add the value of the dividends and other corporate actions to the results from using the actual data. You may even find a way to add any dividends and other corporate action to your results automatically, i.e. any dividend amount added to your total return if the stock is held during the ex-dividend date. If you are using adjusted data in your backtesting this may affect any stops you have placed, i.e. it may cause your stop to be triggered earlier or later than in real trading. So you will need to determine how you will treat your stops in real trading.  Will you adjust them when there is corporate action such as dividends?  Or will you leave them constant until actual prices have gone up? If you will be leaving your stops constant then you should definitely be using actual data in your backtesting to better match your real trading.