Is the diplomacy of the era more like Victorian Era Brinkmanship, post WW1 'Rule of the Victors', Cold War era Us vs. Them, or post Cold War free-for-all?

There are other examples available and these need not be exclusive.

Empires 2 and 3 are high tech powers seeking to expand their political power, often into the same regions. Using Brinkmanship they support one faction against another to create dependencies on their good will.

Worlds Theta and Zed have acquired the technology to destroy worlds, and their historic feud simmers as they constantly monitor one another for any threat that may tip the balance toward one side pushing the button. Half the population is certain it's a matter of time, so while some stockpile what they need to survive, the rest party like it's 1999. Assume everyone is a spy because they probably are.

Culture Alfa put together a winning coalition and after the last war is now economically strangling the defeated cultures. They use this threat to force unaligned cultures to support them.

A web of dependencies, cultural, economic, and military, can make it easier to decide who is where diplomatically.

And Luxemborg can be a virtually unassailable position, until you no longer have money in their bank.