What would the world have looked like?

Okay. No. The Nazis dealt in pseudoscience as much as real science. We captured most of the good Nazi scientists too, so yeah, it wouldn't change much. Technological growth was driven by the Cold War in OTL. Additionally, your scenario itself is implausible. We would have declared war on Hitler, because we were already at war in one theater and the economy was picking up again, and our friends were in danger. If Hitler didn't attack Stalin, Stalin would have attacked Hitler. That was pretty inevitable. However, even if you could get Europe under the Nazis, it wouldn't be a nice place. Sure, the countries would be in greater agreement, but is that really better than having a continent full of progressive democracies who are pretty much in agreement nowadays anyhow, with their populations still in tact? And don't get me going on the fascist economic system. Basically, you have to keep declaring war on everyone. And, of course, fascism would have spread around the world. Things would suck.