One of the processor's tasks is running your operating system and programs. You don't need one of the best or latest processors for web browsing, watching movies, or playing games.
Generation and architecture
Generations and technologies are crucial specifications when choosing a processor. There are exceptions depending on the architecture and generations. Each year new technologies are improving the performance. Sometimes processor manufacturers refresh the processor's architecture a little and sell it. A good example would be the AMD Zen1 (1600) and AMD Zen+ (2600). It was only a minor refresh of the 1st architecture named Zen1. While the AMD Zen2 (3600) and Zen3 (5600) was a new architecture significantly improving the single- and multicore performance.
The processors from 5 years ago are much slower than "low-end / entry" processors today. Here is an example between old and new architecture: AMD FX 9590 (Bulldozer) processor with 8cores 5GHz is slower than an AMD Ryzen3 3100 4 core 3.6Ghz processor.
The Intel scheema for generations is: Intel i9 12900 = 12th Generation 900 Model Intel i7 10700 = 10th Generation 700 Model
For AMD it's similar: AMD Ryzen9 5950X = 5th "Generation" 950 Model AMD Ryzen7 3700X = 3rd "Generation" 700 Model
AMD did mess up their naming because 5950X is the 4th generation, and its architecture is Zen3. The first number in AMD processors indicated a newer generation. Intel did a better job with the naming.
There will be a compiled list for an easier and simpler overview.
Cores (Multicore and Single-core)
Each program and game has a limit of cores that it can access. So only because you buy a processor with 64 cores doesn't mean it will scale the game's performance into an infinite amount of cores. It can be that a program or game stops scaling above 10 cores and additional cores won't affect the performance and in some cases even lowers the performance a little.
For example, if a processor with 1 core is defined as 100% of performance (single-core). Two of those cores won't equal 200% but a little less, 197% for example, with 3 cores it could be 291%, and so on. The reason for this is the synchronization of data between cores and tasks that causes a performance loss.
Single performance is important for most games but also video and image editing. For video rendering, an 8core processor with higher single-core performance is faster than a 12core processor with lower single-core performance.
Frequency / clock speed (GHz)
Most people confuse GHz with performance, like mentioned above, the architecture has a bigger impact on performance. GHz is a good way to compare the single-core performance between processors of the same architecture and generation. Comparing it between Intel and AMD won't work as the architecture is different.
There is also a small catch to the whole GHz part, the Turbo is usually much higher than you would achieve while playing games or rendering. The Turbo clock speed is usually the speed that the 1st core can achieve while other cores run a little slower. So the only way to be sure is to look up some tests. Usually, the smaller CPUs clock better because of fewer cores, but not always.
Disabling HT/SMT will lower the power draw and also increase overclocking stability as it will allow the CPU to clock higher.