Hi
Is there any issue on switching for example from unity ads to revmob to another if there is no video avalaible on current one ¿?
or depending on ecpm on every time on the same app on real time for maximun profit 
lot of thanks
You can using mediation. This basically means you integrate one SDK that knows how to interoperate with a few other monetization platforms. We use Fyber (http://www.fyber.com)