you have good questions, from what I've learned I think you should carry out a test to get answers for your questions. I suggest forward-testing (use OOS in optimizer) because then you'll get a clear hint how your strat would perform in real trading (though setbacks are still possible).

There are many variables which affect the end result, and they seem to be strategy, data, indicator specific, so define your issues, test them, and compare results - that's the best way to get max out of your strat!