I have the British Secret Projects books which are very interesting references (as, I'm sure are the Soviet, French and US versions (although I have the US Interceptors volume too)), both on a technical and political basis. You can see, through the development of the various manufacturers designs a norming of features and sizes. Capabilities and a lot of equipment being set by the Air Ministry.
There's no doubt that there was cross fertilisation and poo-pooing on all sides about design concepts and directions. In the UK, The types of aircraft developed were often led by Air Ministry, therefore much was based around an assessment of a specific type of threat or a specific way of fighting. I guess a lot of the people on here know that only too well. There were also a few privately funded projects with some of the most interesting coming out of Kingston (SABA and X-wing/twin Boom PCB VTOL).
For a long time, I really do think it was a race for each side to be a bit better. In later years I think that there was a strategy to bankrupt the USSR, and some of that strategy must have been reflected in aerospace projects. Problem is, I think we managed to do this to ourselves too!