Russia's tundra becomes arable land, and their fossil fuels become more accessible. Their navy will be able to freely roam the seas when the polar ice caps melt.
Canada will receive the same benefits - enormous access to fresh water, ease of navigation, and agriculturally ideal conditions.
Greenland will have an increasingly large stake in geopolitics, trade, and energy.
China will be less existentially concerned about a blockade of the Strait of Malacca.
[1] https://en.m.wikipedia.org/wiki/Canadian_Shield
[2] https://www.cbc.ca/news/canada/edmonton/wildfires-peat-chall...
And they'll lose.
If you look at the distribution of power, it's not predicted to change all that much. The superpowers are enormously capable of maintaining their grip.
The complaints of poor nations will be met with meager welfare packages and mostly tuned out by the working class of weather nations. It's how the world already operates.
Put the American economy at risk and you get the Gulf War. Attack America directly and you get the Pacific theater.
In any case, none of those particular points matter. No poor country is going to be able to resource starve the wealthiest nations. If they try to invade or block trade, they'll find out the limits of their power.
Several of the countires made "poor" by climate change will have nuclear weapons: Indian, Pakistan, France, Israel, North Korea. You're living in a fantasy. Time to wake up.