Hey Alan,
Have you taken any of Petkos courses? I think form the sounds of things taking a couple could really help speed up your review of EA studio.
As for your question. The generator will generate strategies and then backtest them, if they pass the acceptance criteria then they go into the collection.
The same happens in the reactors but to make it to the collection a strategy must also pass the criteria set in Your selected robustness settings such as Monte Carlo.
I you additionally select to optimize the strategy in the reactor then it will be optimized prior to robustness testing.
In choosing one over the other you may choose the generator if you want to be more manual in how you optimize and test your EAs, or you could save the generated collection and try optimismzing/robustness testing the same collection in different ways perhaps.
Generally I would recommend just I’m using the Reactor with Monte Carlo though, good to have options though. Early days there was only the generator but it’s still there even though the reactor has been added.