Having a lot of room to manuever isn't much good for a force struggling with the issues the Red Army will.
And yes than the Red Army.
Plus, my observation on a 500k army is based on the war's OTL schedule (as stated to another user, I brought it up to address the issue of an all-mechanized German army having the oil if one built an army that wasn't oversized) - and even if it's delayed, better tanks are far from a given.
As for more factories - steel production is 20.7 million (Germany) to the USSR's 16.5 million in 1938.
Picked as the latest year before the war and its consequences render comparisons hard to make fairly.
Manufacturing as a percentage of the world's total is a bit higher than Germany's, but . . .
I'm not sure this translates directly into more war-power, especially with agriculture hurting so badly.
The USSR vastly outproduced Germany during WWII. Granted, it benefited with Lend Lease, so they didn't need to produce trucks and many other equipment, as well as receiving huge amounts of food, and LL might not happen in a delayed WWII, but Soviet production was still huge.
As for tanks... by OTL's 1941 the best thing in Germany's inventory was the PzIV. By that time, either ATL or OTL, the USSR would have the KV1 and the T-34 and neither country would have a war to show them the issues with their equipment, which is specially hard on Germany. Their tanks lacked slopped armor until they've found the T-34 in the USSR.
I fail to see how the Red Army would have a less mobile, less numerous force. It's true the defender, unlike the attacker, has to cover everywhere. But if an attacker can't protect its flanks, a more numerous, mobile defender can very well turn into an attacker. And once the USSR seizes the initiative, it will be the Germans who need to defend everywhere. And they won't be able to.
WWII wasn't like current wars, in which NATO bombs countries with barely any air force, or small countries which lack multipliers like awacs and whose entire territories are under the range of NATO's air power. Nor were ground battles a fight between Abrams pitted against 20 years old export version tanks.
Even in a delayed WWII, Germany would only have a qualitative edge in aircraft, but no way to reach the Soviet factories, and in the ground the technological situation would be one of parity, if not Soviet superiority.
OTL WWII was won by the sides with numbers for a reason.
Sure, the USSR would still be hampered by the Purges but, given time, it will slowly start to improve, as new ranks fill in the gaps.