PRC was never a part of the Warsaw Pact I belive
As time went on, they tried to take an active role over ordering WarPac members around, but the Sino-Soviet Split ended that.
Anyway, let's analyze OTL members:
Hungary: hotbed of resistance to the Russians, not in a strategic location. Can be tossed aside with no real losses. However, it opens Yugoslavia to closer relations with NATO, which aren't so easy for Tito with the Soviets on his border. Possibly too dangerous to throw aside.
Bulgaria: Strategic location, very close to Russia. They're going to be in it unless the West somehow backs up an anti-Russian government there (unlikely with POD after 1945).
East Germany: Leaving aside Russian paranoia about a United Germany, it
is in a strategic location, and I don't see the Russians being happy with the idea of a potentially hostile state several hundred km closer to their border.
Romania: Mildly hostile, not very important except as land route to Bulgaria. I suppose they can be tossed aside, but they have a land border with the USSR, so I think they'll be retained in the WarPac.
Poland: Too important to the Soviets, too close to Russia itself, and, if released from WarPac, too likely to align with NATO. Not gonna happen.
I really can't see the Warsaw Pact getting any smaller than it was IOTL, really. Stalin was just too paranoid about western attacks for any of these nations to drift out of the Soviet sphere of influence before his death, and by then, their Soviet-aligned governments are too deeply entrenched. At most, East Germany will be unified with West Germany.