If Stalin decided to back his fellow "communists" in Asia, would the Allies let that go in order for him to continue the war against Japan, and if they didn't would it end up being like another Korea war, where the Allies and the Soviets bolster the Nationalist and Communist forces respectively with more troops and supplies, or does an all out war break out. Or if Stalin does take the "Big Gamble" do the Allies allow former Nazi's, obviously not the big name ones but Nazi generals and other officials, retain partial control over Germany to fight the Soviets. Does patton remain Military Commander of West Germany? What happens?
One thing we have to remember is that actually Stalin didn't always control the various Communists. He did when they were under the wing of the Red Army, as in Eastern Europe (except Yugoslavia, which had largely been liberated by Tito's partisans with remarkably little Russian help, and was in a position to insist that the Red Army simply transit Yugoslavia without lingering there). Presumably the liberation of China from the north, under the tank treads of the Soviets, would be followed by the imposition of Soviet-approved rule there--that might or might not call itself Communist.
In the scenario I suggest, where before attempting to invade Japan the Western Allies land in south China first (I presume they'd go there because it is a bit easier to get to from established Allied bases in the Pacific and it was I believe more hotly contested by local Chinese than the northern coast nearer Japan), I believe the orders from Moscow for Communist partisans there would be to cooperate with the Allies at least until all Japanese forces on the mainland are eliminated or subdued. (Withdrawal to Japan would be no option to them, or tantamount to suicide, as the USN controlled all the waters around Japan and early Western conquests on the coasts would provide nearby airbases making the isolation of Japan all the tighter.) In general, Stalin spent more time ordering enthusiastic local Communist partisans to stand down and give no pretext of a quarrel to the bourgeois powers than he did ordering them to defy them.
I think Mao and other such independent Chinese Communists, and Ho Chi Minh in Indochina, would find such orders prudent while Japanese forces remained to be defeated. Some, such as Ho, might even seek direct relations with the westerners, if doing so would advance their goals--Ho for instance would mainly want to guarantee Vietnam's (and Laos and Cambodia's, if only to secure Vietnam) independence after the war.
What happens next depends in large part on what the western powers do next. If Americans are fighting side by side with the Viet Minh for instance and it seems obvious to a lot of the US hierarchy that such battles were what won the war against Japan, perhaps the President won't agree to hand Indochina back to the postwar French government and, depending on how far the Viet Minh go in their Communist agenda and how tolerant of this US domestic politics is, perhaps Indochina remains a US ally. Similarly many Americans might see no problem in Maoist demands to at least share power with the KMT post-war. The real struggle in China then might be three-way, between the KMT seeking to suppress all Communists at the first chance, versus both Soviet-controlled Chinese Communists in the north and loose-cannon Maoist Communists in the south; which if either would seek to conciliate Chiang Kai-Shek is kind of up in the air again. Historically Stalin had ordered Chinese Communists to ally with Chiang and Chiang turned on them and killed them, on the other hand this time around Mao might conceivably see American alliance as useful and, protected from Chiang's murderous tendencies by this connection, be the one to denounce Soviet extremism and call for a coalition. Anything like that would be unstable of course; I'd expect though that something that looks stable enough to allow Americans to pull out and go to occupy Japan (assuming they do surrender before an invasion) would get cobbled together by all parties.
As I said, if Stalin does attack Western Allies, east or west, it's a whole different deal. I do think then that Mao would turn on the Americans, unless there had been an open and irreconcilable breach with Stalin already by then, and maybe even then--Mao at least was determined that Communism should advance in China and he could only play the Americans so far. I am not sure which side Ho would wind up on if the Americans had hitherto been dealing fairly with him; securing independence was the first priority for him and if he was getting that from the Americans he might well back them, since after the French and Japanese the Chinese were his next big worry.
So if Stalin goes for it, any Americans still in China would be in big trouble; the KMT would be weak and hardly anything the Americans could back. They might hold on as OTL in Taiwan and surely any Chinese Communist or Soviet presence in Japan itself would be driven out.
As I said before, I think if Stalin did something that wild, the Americans could and would rearm their recent Axis enemies, taking as much care as they could to forestall a simple return to the old regime of course, but yes they'd use Germans and Japanese against the Russians and they'd probably cooperate pretty well, as they'd be defending themselves and their homelands.
But since he'd be facing that, with the entire US wartime economy backing them up, I don't think Stalin would take this gamble. He'd know it would make a difference to his own Red Army and to the peoples they might occupy, who started this particular round of war. He'd know the Americans would be unlikely to trust him if he called for a truce, and that it would be hard to persuade Americans by even the cleverest propaganda that he was any different than Hitler and so they'd keep fighting.
It's possible even Mao would desert him at this point, if the Americans were tolerant enough of the prospect of a Maoist China.
So I think Stalin would stand pat, wait for quieter methods to edge his agenda forward while taking advantage of opportunities--up to but not including the risk of open war,
I do not believe he avoided that OTL merely because of the Bomb. There was little to fear from American A-bombs just after the war, and not that much to fear even as late as 1949 when he had his own. It was the overall power of the USA he worried about, and even after the standing armies were largely demobilized, the Naval projects put on hold, the air forces scrapped and downsized, he still had that to worry about.
If in an A-bomb free world he would attack eventually (and I am not at all sure he would ever) it wouldn't be right away. Something like the Korean War might be the right time--recall though that's half a decade later.