can you run something off an ac dc adapter if reqires less power or will put out more than it needs?

Answer 1

If the dc output is within a reasonable range, that is no problem if the current rating is high enough. Don't try to run a 3.5 vdc item on a 12 vdc output, for example. You can use (in most cases) a 9 vdc on a 6 vdc product though.