I have recently started using search and for me autocomplete works. If I enter part of the word or phrase, it does give me a drop down with matching options. I also use the plugin searchform, so not sure if that enabled it.
To know more about Dokuwiki search, this might help:
https://www.dokuwiki.org/search
And here's more about templates.
https://www.dokuwiki.org/template
Hope that helps.