Question: Do people who sing with lots of power have a smaller vocal range? I have heard that if one sings with power, eg like an opera singer, you will get a smakler range. I feel that the more power I use the harder it is to sing higher.
Is there anything ti this?

Answer: 
It's always hard to define such words as "power"... But if you mean with it, that they can sing stronger, louder tones, I would say definitely that the range isn't affected by the fact with how much 'power' you sing.

If you sing louder, with much pressure, you may be running out of breath sooner, because you use more air when singing that way, but the vocal range itself isn't affected by this. 

Just hum quietly and go as high as you can. Now stop and sing the same note with open mouth and 'power'. You could still reach the tone right? You probably just couldn't hold it just as long, because you used way more air that way ;)
No they don't. This is a bizarre claim, and if the person who made it has evidence - let's hear it!