I actually did quite a bit of research into this issue for an honor's thesis I never was able to write. Most of my knowledge comes from the 1980s, but I can touch on the other periods. I don't have my source list in front of me right now, but I can supplement later.

Each side approached the issue of conventional forces in Europe from a completely different perspective. The Soviet Union and Warsaw Pact kept substantial numbers of conventional forces in the theater all throughout the Cold War period. The bulk of the front line troops were of the Soviet Army, and generally were the best formations in the USSR. Forces of the satellite nations were also present in-theater, but they tended to be stationed in their own countries. The DDR, Poland, and Czechoslovakia had decently-sized conventional armies at their disposal. Soviet doctrine called for their use mostly to secure rear areas and pacify conquered territory, to free up the more politically reliable Soviet units for offensive operations.

Generally speaking, Soviet doctrine called for the combined use of conventional and chemical weapons to facilitate an invasion of the West. This never changed even after the introduction of nuclear weapons to the theater, and Soviet policy was against first use of nuclear weapons, even on a tactical basis.

NATO, in contrast, had a constantly evolving doctrine. In the beginning, in the 1940s, the countries of Western Europe were not in much of a position to field a conventional army and we're still recovering from the Second World War. The US, UK, and France maintained occupation forces in Germany, but at this point these were not intended to seriously oppose a Soviet invasion, but to act as a tripwire, which would trigger a nuclear response. American doctrine in the 1940s, and through much of the 1950s, relied almost exclusively on nuclear weapons as a deterrent against Soviet aggression.

It was not until the 1960s that NATO began to reevaluate this strategy and actually take conventional forces in Europe seriously. The US and UK were by far the most serious about this, and had the most troops stationed in Germany. Additionally, in the 1950s, NATO made the decision to re-arm West Germany and integrate the new force (the Bundeswehr) into the collective defense effort. This was a significant development because it opened up a large source of manpower that had previously been closed off to the western alliance. On the flip side, France withdrew from the integrated command structure of NATO in 1966. France maintained its presence in Germany (more on that later), but actively fostered uncertainty as to whether they would fulfill their treaty obligations should hostilities ever break out. We know now that a series of secret agreements were executed by the US and French governments that if the Soviets did invade, France would in fact rejoin the unified command structure and stand with the rest of the alliance. The Soviets did not know this, and a decent chunk of their strategic planning was dedicated toward attempting to widen the gulf between France and the rest of NATO, and keep them on the sidelines of war broke out.

Things began to slide back down, as far as the west is concerned, through the 1970s because of the Vietnam war and the substantial drain on manpower and morale it had for American forces. This only began to shift again in the 1980s when Reagan was elected, and emphasis was again placed on defense and military preparedness.

Overall, the Warsaw Pact maintained a substantial numerical superiority in Central Europe at all times. While they paid lip service to the idea of defending themselves from a potential invasion, an examination of their strategic planning and doctrine during the Cold War reveals that their mindset was always on the offensive. By the same token, while NATO drew up hypothetical plans for offensive operations in Eastern Europe, these were not serious and the entire focus of the alliance was on collective defense against Soviet invasion.

I'll write on actual capabilities, plans, strategy, etc. next.

Generally speaking, NATO formations in West Germany were deployed in two army groups--Northern Army Group (NORTHAG) and Central Army Group (CENTAG). NORTHAG was made up of primarily British (the British Army on the Rhine or BOAR) and West German units, along with Dutch, Belgian, Canadian, and Danish troops. It's area of responsibility ran from the Baltic Sea to an area roughly around Frankfurt.

CENTAG was made up entirely of American and West German troops. French forces were concentrated in southwest Germany near the French border.

The British and German units were stationed in their forward positions almost full time. About half of the American forces were always in-theater, while the other half were kept in the United States, with the objective of flying the men across the Atlantic to meet up with pre-positioned equipment in the event of a war warning. The smaller allies tended to keep their troops away from the front, and often inside the borders of their home countries. The idea was that if hostilities looked like they were going to break out, they could be moved up to the front in time.

The overall doctrine of NATO forces was based on the idea of forward defense. In the event of Soviet attack, NATO units would resist the invasion as far forward as possible, and give ground only when necessary. The goal was to attrit the invading forces and make the attack too costly for them to succeed. Further, the goal was to trade ground for time, and slow the Soviet advance as much as possible to buy time for equipment and manpower reserves to be mobilized in the United States and transported across the Atlantic for an eventual counterattack to drive the invaders back.

Soviet doctrine was based on the concept of "deep battle" that had been developed by the Red Army through the course of World War II. Initially, the Pact forces would conduct a general attack across the entirety of the inter-German border. Once weak points were identified, those areas would be reinforced with the objective of breaking through NATO's defensive line, wrecking the rear areas, and rolling up the rest of the NATO line from the flank and rear. Additionally, the Soviets invested large resources into their submarine fleet and naval aviation fleet with the intent of closing the Atlantic and preventing American forces from reaching Europe.

NATO was of course aware of this, and by the 1980s had invested large sums in trying to offset the Soviet numerical superiority with technological superiority. NATO equipment, especially that of the US, UK, and West Germany, was objectively superior to that of the Pact in many ways. The question of whether or not it would have been enough is an open question that thankfully we never had to find out the answer to. Fiction writers loved to get at it though, and there were some good books written in the '80s that covered a variety of outcomes.

I'd be happy to go into more detail about what I know if you have more specific questions.

In the early 80's the US finally discovered that the arms race against the Soviet Union actually only had one runner. The Soviet Union made some early advances with captured German technology but spent much of the 60's 70's and early 80's simply stealing US technology. The Soviet Union hitched a ride with the US and it took the US 30 years to figure out why the Soviet Union was always just behind on technology.

1985 report about Soviet Copying of US equipment pdf file

You might find this 1983 documetary useful: Keeping the Old Game Alive

I think Tom Clancey's Red Storm Rising did a good job explaining this.