First I am dubious about calling it a world war, the circumstances for WW2 would not be present, in fact minimal butterflies would create a different geopolitical background for conflict. And I would argue that the antagonist will not be Germany unless one assumes it goes revolutionary communist and pursue a different trope.
Germany will be moving towards an even more liberal democracy within its existing constitutional monarchy. Policy will be guided by the desires of the SPD, Zentrum and the Liberals, more the left-wing, but I would see a lot more influence from the liberal right here. This is an industrial nation seeking resource imports and export markets, its diplomacy will be containment of Russia should it stay revolutionary and deter France, seek detente with the UK, seek "alliance" with the USA and otherwise gain allies/trade partners among non aligned states. Its other problem child would be a Fascist Italy. And that leaves a lot of complex plot twists out.
Japan likely stays aligned with the UK but has strongly opposing interests in China, its goals still put it on track to becoming an enemy. But here the UK has a real competitor existing in Gernany and may appease Japan more, it may further acquiesce in Italian ambitions, or seek relations with Russia to offset Germany. One might see a lot of unrest in whatever happened in the OE.
Germany might join the USA as an "open door" club member in China, both have incentives to break the British Empire and even to breakup the French Empire. They will compete in Latin America but globally they have much in common. Or Germany could seek resources and market in Russia. It should rebuild its trade in China.
If you want the most likely two friction points it will be China and the OE. Both have British ambitions versus German interests, both draw in the other powers. But frankly I would not lightly predict another Anglo-Gernan war. Indeed I would be hard pressed to find too many points where friction heats to war even as in OTL it flowed so easily. I think one must be creative, deterministic or unlucky to spark any war significant enough to tumble all the players into it.
