IMO no Resistance forces were capable of defeating German garrisons on their own.
Also, as of 20 July Allied armies were poised to sweep over large sections of the Nazi empire.
OTOH, Germany did withdraw from Greece in October 1944; the Communist wing of the Resistance tried to take over, until British troops landed and restored the monarchy . It's quite possible that the post-WALKURE regime evacuates more territories sooner, creating more opportunities like Greece.
IMO, the most probable areas of withdrawal would be France and Italy.
In France, the Allies were about to break out of Normandy and drive to the German border; one presumes they would follow close behind any German retreat. And "Free France", headed by De Gaulle, was already ruling all French colonial territory (except Japanese-occupied Indochina, Corsica, and Algeria (then considered part of France proper). Also, there were Free French troops in the Allied forces: an armored division which landed in Normandy on 29 July, and an entire army which landed in the south on 15 August.
As to Italy: as of 20 July, the Allies had already occupied most of Italy: Sicily, Sardinia, and the peninsula up to Tuscany (Florence was liberated on 23 July). The authority of the Italian state under the monarchy had bee established in this area. The Allies were pressing forward, and would closely follow any German withdrawal, leaving no real opportunity for Resistance takeover.
The Yugoslavian Partisans, I guess, would have a chance to liberate the country on their own. But they took over OTL anyway.
There was no Resistance in Hungary, Romania, or Bulgaria. In Slovakia, the troops of the puppet government rebelled against the Germans on 30 August. The Germans suppressed this rebellion by 28 October; ITTL it would probably succeed. (Soviet forces were only a short distance away across the Carpathians. Amazingly, the Germans held off Soviet attacks while the Slovaks were raising hell in the German rear.)
In Poland... The Home Army rebelled and seized Warsaw, but were put down by the Germans, even though Soviet forces were just to the east. (Though to be fair, those forces were exhausted and out of supply after their advance of nearly 300 km, and had been met by strong German counterattacks.) ITTL, they might hold Warsaw, seriously changing the dynamics of Poland's liberation. The Home Army was loyal to the Polish government in exile.
Resistance forces in Netherlands, Denmark, and Norway were wholly loyal to the governments.