The XLSForm template is the authoritative, maintained reference around differences between ODK Collect and Enketo. It replaces the XLSForm website reference table which was not very consistently maintained. The only missing item from the XLSForm template that I'm aware of is table-list as we discussed in XLSForm Template - Few missing Appearances. The template is linked to from https://xlsform.org/en/ref-table/ and https://docs.getodk.org/xlsform/
The first document you link to is the best high-level summary of the major differences that I'm aware of. We use the first section as our "north star" when thinking about alignment work. If there are items you think are missing, please highlight them in this thread. We try to keep this list to big themes.
The two major items in the differences list are bugs around nested repeats and read-only being static. The source of these issues run deep in the engine implementation and are connected to other concerns like performance. We have been actively working to identify a way forward to addressing them holistically rather than making piecemeal patches as we had previously been making. We're not entirely sure what the approach will be yet but will be talking more about it in the new year. We are also looking at strategies to further align the user experience.