A important aspect is that while Russia would be the biggest winner in demography and economics in no World Wars, they wouldn’t be the only ones, Germany and AH would both have over 100 million people each, France would likely have a population of 70-80 million people and that’s if we ignore their empire and the positive and negative of this. UK would likely be similar in population as in OTL, but with UK still being the main financial center of the world, their deindustrialisation siuld likely have been less painful.
Canada, Australia, South Africa and New Zealand will also all have received much more European migrants, and thus would likely have higher populations. Less diverse, but higher. There may also be a boost to these countries, and the US and Latin America, when the greater number of white settlers in other colonies largely leave during decolonisation, which I'd expect by the 80's and 90's at latest, if for no other reason than that indirect control is significantly cheaper than direct rule. If Britain binds the dominions more closely, either as allies or in an imperial federation, they'd boost Britain's power and influence significantly. Without the world wars, the myth of empire and the identity as Britons overseas isn't discredited, or is less discredited. Additionally, the colonies would be a boost the population of London at least, as it'd be
the world city to people from the Empire, its position as a centre of trade, finance and culture unchallenged by New York.
The cultural and scholarly importance of Berlin would be undamaged by the wars and Nazism, and it wouldn't be divided, so it'd be bigger to. Italy, meanwhile, would probably continue its prewar migration patterns for a bit longer (young men, usually from the mezzogiorno, go to Northern Europe or the Americas for work, save up enough money to buy land, then return home and buy land) and without fascism Italy would urbanise sooner (fascist Italy discouraged urbanisation because unemployed and underemployed rural people are easier to brush under the carpet and ignore than urban unemployed and underemployed people, who tend to form mobs), and probably in an even more uneven way than it did OTL, when there was at least some effort to encourage industrialisation in the South post war. That said, without the depression, perhaps sustainable industries might be able to develop in the South, redirecting migration towards Naples, Catania and other southern cities. Much depends on how the government in Rome plans for the future. Either way, Italy likely has a higher population, and thus more weight to swing around.
France definitely has a higher population without losing so much of two generations of young men. They also probably keep at least some of Algeria, giving them a foothold in Africa and reason to be wary of any attempt by the Turks to use Islam as a political tool. They may also try to integrate more overseas departments than iotl. Depending on how it's handled, and how tightly France tries to hold onto her colonies, this could either be a boost to their power or a lengthy quagmire that entangles and distracts France for a generation or more.
The Balkan nations will also have higher populations, and thus more influence and likely more advanced economies. Depends really on whether the region remains relatively stable with occassional squabbles leading to either diplomatic spats or short, sharp wars, or is a perpetual hotbed of conflict and proxy wars.