Might as well cover all topics.

Custer? It is not a choice between competence and heroism. He was superbly suited for field officer as combat was then conducted. Not well suited for staff and planning activities and above.

The perfect war for him was the Mexican War, but he missed it. By 1861 he would have been a General. In the East he would have screwed up a few battles and been eased out. In the West he might have done better in the more chaotic warfare of Missouri and Arkansas.