Nuendo 5.5.5 on win 7 64 OS

I am new this forum.We bought nuendo 5. I installed it on win 7 64 bit OS.Black magic intensity card will be used for video out.What do you recommend for working best performance ?which video format do you recommend?

We have very little problems with most of the relevant video formats, here.
Our most often used and well perfoming format is H264.
It works via Intensity and native.

Big K