What do you mean by "dark side"?
Backtesting is what it is. Dewars can make process bit more pleasant but wont help much with overall results, imo.
I humbly suggest Derwas without any backtesting - to increase pleasure and overall wellbeing.
By "dark side", I'm primarily referring to the "curve fitting" conundrum. Where we are aware that we are subject to curve fitting, yet participate anyway, thinking we have a clever angle where our changes are expected to benefit out of sample equally.
Determining, then modifications based on the "why" to implement the "what" instead of merely altering the "what" to improve the PnL is not always intuitive.
I'm guessing the multidimensionality of options gives more opportunities to curve fit compared to equities, futures, etc. Besides the price movement of the latter there are all the permutations of volatility that the former add to the mix. It seems you could easily end up making changes that improve the performance for some regimes and make it worse for others.