ASB, but here's how I see it.
Regarding the USSR, there would be no war crimes trials. Anyone remotely associated with the Soviet government,military leadership, and communist part organization would be summarily executed. Period. Russians were subhumans after all so there is no reason to placate the subhuman masses with the pretense of legality.
I think the UK and US would be treated differently. Nazis would have the same overall goal in mind (complelete elimination of any political/military/social source of opposition), but since both the US and UK were seen as more racially acceptable, at least at the Anglo-Saxon upper echelons, the Germans would seek to offer some legitimization of their elimination. I suspect key civilian leaders like Churchill, George VI, FDR, and their closest advisors and supporters, etc. would conveninently be killed attempting to avoid capture. Military leaders, such as Eisenhower or Montgomery might be offered parole in exchange for retirement, but many others like Bomber Harris and a host of other RAF, USAAF, and USN personnel involved in the aerial bombing campaigns, the naval blockade, submarine warfare, intelligence/propaganda might well be tried as "war criminals", perhaps fairly openly and even fairly to help convince the new subject populations that their leaders deserve what the Nazis intend to do to them.