Placing cubes is optional, and you gain no advantage by doing so “in advance”. The conditions for activation are to have at least one cube and the most cubes, but ties count as the most and although you can only place on one character each turn, you are not limited to placing only one cube.
The troubleshooter already has an activation marker on her (yours), so will be exhausted and only take one action if you activate her.
Since you posted your turn as a question, please confirm or modify your turn now you have answers (and ping me when you edit).