For the latter point, have you seen: https://www.dokuwiki.org/plugin%3Alogger
? I have a page a year with the format:
====== User logs for 2020 ======
//Although sort markers do not show, this table is sortable.//
<csv admin:logs:2020.csv delim=; hdr_rows=0></csv>
If you do this you'll also need the csv[/m] and [m]sortable
The users.auth.php[/m] file is formatted as: [m]login:passwordhash:Real Name:email:groups,comma,seperated
. The "login" field must be unique, but I can't see anything that ensures the other fields are unique, they are just lookups. Perhaps Andi or one of the other experts can confirm this.