I belive it's hard to put to gether all the details at one place between one version to another. I know this will not the answer you are looking.
Since I'm part of Pega CoE at my organization, I had interactions with different internal customers who are using Pega for a different need and a complete differenet features as compared to other customers with in the Organization.
Hence on a year to year basis, we started Publishing a Hiigh Level Road Map and Recommendation document where we will be publishing the existing capabilities of Pega for the version that application is using Vs what are the new features avaible in the latest version of Pega in that space, which also gives an idea to the application management to understand the capitalizing the investment on Pega i.e., if a feture is avaible for the current version, but not actively used by the application team.
For one of the Pega v7.4 application, which uses Pega Express Features and other Low Code Capabilities, hence we prepared list of features and enhancement included in the latest version of Pega's App Factory/Low-Code Model and other DevOps enhancements in the details. While publishing the recommendations,we always include the common fetures which are introduced in the later versions for that app. Eg.Containerization for Application Deployement is started with Infinity Series, which is not there in Pega 7.4
Hope this gives an idea on what features you can focus and get better understanding on Version to Version changes.