Some really great questions here! Let me try and answer them:
A. Record geometries are generated as the union of parcel feature geometries associated with them. As long as you have your parcel features correctly assigned to a record (e.g. your parcel features have a GUID value in their Created By Record field that corresponds to the correct record feature), you can use the Build Extent editing tool or the Build Parcel Fabric GP tool to update record geometries according to the updated parcel geometries.
FYI - the Build Extent editing tool runs on a maximum of 1,000 features in the active map view. If you want to update more than 1,000 features or features outside of the active map view, then you should use the GP tool.
B. Historic parcel features are created automatically when performing record-driven parcel edits (here is a good video introduction to these workflows). In the database, historic and active parcel features are stored in the same parcel type feature class (lines or polygons). Pro's Parcel Fabric uses a definition query that points to the Retired By Record field to determine whether a parcel feature is active or historic. Now, I think some of the other bullet points in your post point to a really interesting question related to adjustments, alignment, and topology in the parcel fabric: by default, least-squares adjustment tools in the parcel fabric use measurements for both active and historic parcel features to find residual measurement errors on parcel line features. In other words, adjustment tools will affect both active and historic parcels. Alignment tools and topological editing workflows behave similarly.
If your question is how to preserve the original data inputs that contain misalignments, you could utilize some other strategies for doing that: exporting, appending, or using Copy Lines To to add new features to a different feature class (or parcel type if you need the benefits of the parcel fabric for managing your data).
C. The best free resources can be found in ArcGIS Pro Parcel Fabric Videos Place on Esri Community and through the Parcel Fabric Meetup. There you'll find all kinds of great video resources to help you learn about many different components of the parcel fabric. The Meetup can help you stay up to date on all things parcel fabric. Esri Training has some free resources, and also offers a 3-day instructor-led course on the Parcel Fabric where you build a fabric from the ground up.
D. Records exist as the digital representation of legal descriptions in the GIS. What you're describing in this example is a quality-driven edit (here's a helpful video on the topic) updating parcel feature geometry to ensure connectivity or spatial accuracy. For quality-driven edits, you do not need to create a record.
If you want to add notes about a quality-driven edit, the first idea that comes to mind is to add an attribute field where you can document changes you've made. Selection tools and the Attributes pane could then be used to update attribute values for features you've modified at one time.
Others might have a better idea for handling this kind of process.
