Yes, there's a possibility of using too much energy. The Buddha uses the analogy of tuning a stringed instrument. If one tunes the strings too tight, the instrument won't bring forth beautiful music, if one tunes it too loose, it won't bring forth beautiful music. But if we tune it just right, the instrument is capable of bringing forth beautiful music. The too tight often comes from wanting to achieve, and we can balance that by learning how reflect on cause and effect. The too loose is not enough energy, letting the mind wander and drop into laziness.
And is a dream journey and a meditation experience the same? I don't know what a dream journey is. As to the meditation being more passive; the meditation we teach is certainly not passive, it's very active because we are trying to develop wisdom. The object of our meditation is to develop wisdom. So it's a very active thing. We are not just concentrating, and thinking wisdom will come by itself. We have to be active and investigate into the arising and passing of the experiences and this depends on having mindfulness and awareness.