There are some specific unit setups that don’t require all slots for the given hero given some specific situations, so you might want to deselect units. It’s good to have options. About deselecting powers it’s not for Ajax GK since as GK he only uses Frenzy. Deselecting powers is helpful for, say, when you want ot use AP with Ajax you don’t want him to use Whirwind for … many reasons.
I’ve seen so many different opinions about AP vs. Manual. Many complains about how dumb AP is. Some other opinions make me think that they are contemptuous of AP. Some even suggested removing AP from the game, as if manual is the only true way of playing. For me both modes are tools and have their use. It’d be nice to be able to play faster in manual since it’s the true drawback of manual compare to AP. Otherwise it’s situational, the right tool for the right situation, depending on your purpose. Let’s not forget that Odyssey today can cost up to 18M Gold per adventure. Good luck doing that with 100% manual, even with some bonus. On the other hand, if you want to have a chance to beat Blöffer’s GK, good luck if you AP his base.