I think Putin will most likely prefer to annex almost all of Ukraine and land that is not historically under Russia will be ceded to other countries. Having a proxy/rump/puppet state next to countries that are aligned with NATO can still bring unpredictable results and it's best in Russia and Putin's interests to have full direct control over them.
For example, even though President Lukashenko of Belarus is now in our eyes a Russian puppet since the pro-Western protests in 2020-2021, he wasn't always supportive of Russia, as the relationship between Russia and Belarus was always unpredictable, such as the
Milk War, the Belarusian response to Euromaidan, and Belarusian authorities arresting Wagner PMCs. When Lukashenko falls, Russia will most likely attempt to annex Belarus.
Here are the two maps that will give more clarification to the annexation scenarios.
View attachment 4684345
View attachment 4684353
Oblasts are usually named after their cities.
Russia
Russia is most likely to annex almost all the oblasts that are labelled in green. Russia will definitely take the city of Chernihiv (renamed to Chernigov from Ukrainian to Russian) because it was an important city back in the Kievan Rus and medieval Russia, so annexing Chernigiv will be a symbolic victory. Putin and Russia will definitely annex Kiev because taking the capital of the former Kievan Rus will give Russia the legitimacy that it desires to state that the Russian Federation is the only contemporary successor to the Kievan Rus, and thus Russia represents all Eastern Slavs because of it. I also think Kiev will become a Russian federal city due to its strong importance in the sense of Moscow, Saint Petersburg, and Sevastopol.
Moldova
With the pro-Western government of Moldova collapsing due to pro-Russian protests and unrest in the country, Putin can seize the moment of gaining a pro-Russian ally. In addition, Moldova has not joined NATO yet, so that may be a detriment to the country as most pro-West and pro-Ukrainians can say that Russia will attack Moldova after annexing Ukraine if Moldova decides to join NATO to represent pro-Russian Transnistrian interests.
To keep Moldova to stay in favorable terms with Russia, Putin can cede the western half of Odessa Oblast (with cities like Tatarbunary and Izmail renamed to Tatarbunar and Ismail/Smil respectively from Ukrainian to Romanian) and Chernivtsi Oblast (with Chernivtsi renamed to Cernăuți). The western half of Odessa Oblast will be such a benefit for Moldova as Moldova is a land-locked country and giving them access to the Black Sea with ports like Tatarbunar will definitely make one of the poorest countries in Europe wealthier.
Hungary
Hungary is one of the pro-Russia EU allies within NATO thanks to Viktor Orban's sympathies with Russia and Putin and his obvious contrasts in policy-making with other leaders of EU countries. In fact, he's really a politician based on realpolitik. Russia giving Zakarpattia Oblast to Hungary under Carpathia and giving the historically Hungarian city of Unhhorod to Hungary as Ungvar will make Hungarians very pro-Russian, putting Hungary in Russia's sphere of influence and having that type of country inside of the EU and NATO will be very interesting.
Poland
Putin giving 5 of the historically Polish provinces of Lviv, Volyn, Rivne, Ternopil, and Ivano-Frankivsk to Poland is a risky move, because Poland and Poles in general fucking despise Russia and Putin for obvious reasons. I doubt giving those provinces to Poland will decrease
Russophobia Russomisia within the Polish populace. Poland is very pro-America and pro-NATO that they will put weapons and missile systems inside the provinces as a deterrent against Russia.
Maybe more Poles will like Russia because they are honoring their borders by giving them land that they took when they were the Russian Empire but the risks are too significant for Russia to give those provinces to Poland. Most likely, they will keep them unless Poland and Poles change their tones towards Russians.
Conclusion
I think we live in a time where annexations and empires will be the next trend that many countries will follow. Annexation is such a good strategy in Russia if they are to win the invasion of Ukraine because they get the symbolic cities of the Kievan Rus, and cede land they don't need to make Russian allies.
I doubt anyone will rebel against the Russian government over what is formerly Ukraine because rebellions and protests these days don't fucking work. If China can suppress the Hong Kong protests without consequence and Assad can stay in power without losing any after a civil war, then any country can at this point. Authoritarianism and imperialism is growing popular due to weak-willed people and there will be countries that will cede to exist in the upcoming years.