I always interpreted 何 as "what" and "どう" as more of a "How or How about?" and thus was under the impression that if one wanted to ask "What will you do?" or "What did you do?" you would say 何をしますか ...
I've read on Stack Exchange that どうやって can be used to mean "what did you do in order to x" どうやってお医者になったか? — What did you do in order to become a doctor? This definition makes a lot of sense to ...
I would like to know if there is a shift in nuance in questions such as these: 誰が参加したんですか。 vs. 誰が参加しましたか。 いつ着いたんですか。 vs. いつ着きましたか。 I wish to limit discussion to only non-yes/no questions ...