I understand the focus of your post but point out a technicality.
By 1945, the Kwantung army was just a shell of it's former self having had it's best units stripped from it and sent to fight the allies.
In August 1945, the battle hardened Red Army did take on the Kwantung army and cut through it like a hot knife in warm butter.
Even at full strength, I don't believe the Kwantung army could have put up much resistance against the Soviets since it never had the sort of heavy weapons required to deal with red armour.
Someone here at FR, perhaps yourself, posted a great summary of how the Soviets transported tens of thousands of their troops from the Eastern front to Manchuria, etc and surprised the Japanese forces there, decisively defeating them.
I was referring to other Japanese armies (full divisions) further into the Chinese Mainland. Don’t have a good source on how many but it was significant. Remember the Japanese literally got into India and had taken-over much of Burma, Thailand, and some of Vietnam.
If these armies decided to put up a suicidal last stand, then our casualties and those of our Allies coming in from India/Burma and fighting across the mainland would have been horrible.
Remember, Mao kept most of his Red Army in reserve, letting the Nationalists do most of the fighting and dying in great numbers (millions) against the Japanese. Mao intended to use them against the remnants of the Kuomintang forces after the defeat of Japan, and that is exactly what he did.
If anyone has an Order of Battle for mainland China Japanese forces, please list it or give us a source. A little known theater of combat that really does need to be learned.
PS: One of my late friends, Gen. Bernie Yoh, Kuomintang guerrilla forces leader, becamethe youngest of their generals for his heroic and smart defeat of a major Japanese force where he used his head instead of guns to drive them out of a major ammunition depot/city. See “SACO: Sino-American Combined Operations” book. There is a full chapter on Bernie, who later fought in So. Vietnam under Gen. Ed Lansdale’s command.
Also, remember, Kuomintang forces defeated a major Japanese drive in Burma that would have opened the way to a major invasion of India. Our Air Force, perhaps the Flying Tigers or reinforced 8th AF under Chennault provided the air attack, but the Chinese on the ground took on and defeated a major Japanese army.