Any analogy which is helpful I see in Poland
Now that is quite interesting. I didn't know this about Poland!
Of course to do this, we might need Lenin living longer, or someone else taking over other than Stalin, or maybe, maybe a relatively unified Politburo which stands up to Stalin that we're not going to do collectivization, and this evolves to a strong Politburo-weak chairman system. Might be enough. I mean, Stalin really was a nut and I think meets the clinical definition of a sociopath.
Stalin was definitely paranoid. But I am not sure how many people would be able to avoid being paranoid in the same situation. If you've not read Kotkin's biographies of Stalin or listened to any of his talks on Stalin I very much recommend his work. It certainly makes a compelling argument that there wasn't anything inherently broken about Stalin - but rather he was a human being with too much power and too much belief in his ideas.
As to what might happen if the rest of the Politburo told Stalin "no" about Collectivization - I don't think it would be the change you think. Stalin does not seem to have forced through measures that were strongly opposed by the Politburo. So if the Politburo opposed him and remained opposed to him over Collectivization... Well, he may well have just focused on other priorities. And I think to get a strong Politburo and a weak Stalin you need to radically change the personalities involved or have Stalin not be general secretary of the Party either because Lenin never gives him the job or the Politburo accepts his resignation over the supposed letter of criticism Lenin wrote.
he probably can't pull off the Holodomor in which an existing famine was intentionally focused on the Ukraine
The Holodomor also devastated southern Russia.
What if Stalin didn't collectivize the soviet agriculture? How might have it changed this country? What about agricultural productions? Famines?
Firstly, there's the question of how we avoid Collectivization. Let's say that Bukharin manages to convince Stalin that the time is not yet and that Collectivization should remain a voluntary process until the country is more prepared (so some point in the 40s). Of course, before that can happen, WW2 happens, and in the violence and then the painful reconstruction afterwards, Stalin never does feel the time is right, and after he is dead, his successors are too cautious to push the policy through, even though it remains a goal of the Party in theory.
Potentially, this is a colossal change. It's hard to say exactly however, since so much information is still hidden in those parts of the former Soviet archives that are still secret. If indeed the full story ever was committed to paper.
Firstly, it's important to recognize that no Collectivization does not necessarily mean no de-Kulakization. There was real anti-Kulak sentiment among the bulk of the peasantry (who had not done so well during the NEP) and the anti-Kulak campaign may well have partially been aimed at increasing support for the Party among the peasants by hammering down the "sticking out nails" that were irritating their communities. Similarly, the Soviet regime is still likely to be cracking down on what they termed "economic criminals" - which could either be unscrupulous profiteers or honest businessmen who happened to get on the wrong side of their communities or the local Party (a campaign which hit the Jewish community in the Soviet Union hard) and the Soviet regime is still likely to engaged in forced resettlement of groups.
Secondly, even without Collectivization, there is still likely to be a famine due to the poor infrastructure in the country and due to several years in a row of bad weather. Likely it kills only thousands or low hundreds of thousands of people however.
Thirdly, if Allen is right in his book Farm to Factory, a continuing NEP means slower growth rates in the early 30s, but faster growth in the late 30s, meaning the USSR would be only slightly behind the OTL USSR in terms of industrial development in 1941. Likely that means that the Red Army can't get as many weapons in the mid 30s as OTL, which could be a blessing in disguise given the rapid changes of military technology in the 30s. Or it could lead to the Red Army being just weak enough compared to OTL that the Germans can do that little bit better during Barbarossa... Where that goes is hard to predict.
Fourthly, Stalin seems to have been really hurt by how much criticism he got for seeing Collectivization through - he'd taken the universally agreed policy of the Bolsheviks and implemented it for the good of the people. And in return he got flak from the Party and unrest in the general population seems to have shot up. And possibly, elements of the military were so horrified that they began considering a coup. It may well be (though all the evidence we have is circumstantial, if this can be proven definitively, it can only be done with access to the KGBs internal security archives) that the backlash to Collectivization directly caused the Purges - at least the Purges as we know them. As we know, the Purges gutted the Red Army, the Old Bolsheviks, the rank and file of the Party itself and the general population. It was a disaster for the country and especially the Party itself, and it did much to horrify and repel foreign observers - directly contributing to the Soviet diplomatic isolation in the late 30s, which of course led to the Hitler-Stalin pact of 1939. We can't say for sure, but it is very possible that no Collectivization would mean no Purges (though lesser purges where the purged are fired, not murdered, as Lenin did after the end of the Civil War and systemic violence like the anti-Kulak campaign are still very likely to continue through the 30s and 40s), a stronger Red Army, no Commissars crippling the ability of army officers to act decisively, a stronger more ideologically diverse Party, and a stronger population.
Fithly... I started off saying that Collectivization could be put off until the mid-40s and rendered moot by WW2... But what if the lack of Purges means WW2 is avoided? What if the Soviet Union becomes an ally of Britain and France in the late 30s and the trio contain the forces of Nazism successfully without a major war? Well... We may have just postponed Collectivization. Even with the NEP proving fairly successful as an interim measure, no Bolshevik, not even Bukharin, wanted to keep the NEP going forever. And I am just not aware of an alternative they discussed other than Collectivization like that in OTL. It may be that postponing it means the worst of it is avoided though - if Collectivization is done during good years, and at a time when the USSR has better transport networks, greater wealth, better foreign relations and greater institutional strength... Well. The exact same policy aims, enacted with the exact same ruthlessness, might still produce radically different outcomes. But maybe the Collectivization campaign happens during bad years as it did in OTL, just later on, and millions still die.
My gut feeling is that things go much, much better for the Soviet Union if there is no forced Collectivization. And things are much better for the rest of the world too. But there are ways that worse outcomes or indifferent outcomes could occur as well.
As far as agricultural production and famine... I don't see there being much difference in overall agricultural output, other than the Soviets avoiding the artificial depression that Collectivization caused. Soviet farms may be less labour efficient and Soviet cities more labour efficient through the 30s and the 40s (due to more people staying on the land for longer). There will be a famine in the early 30s, but it would be much less severe. Depending on how WW2 goes, if it goes at all, there may be another famine in the late 40s.
fasquardon