The auto kill option works best if you use it to farm the bosses every 5 levels.
I used the max souls option once but it made things boring. Max cash was the right amount of help without ruining all future runs.
Agreed, to keep the game fun, you should only use the extra money option, as soon as you do the unlimited hero souls, there is no point to playing anymore and you can't get rid of it unless you import an empty save or do a hard reset.