>I am not sure how many of the commands have been converted
There's a page [1] on the FreeBSD wiki with a list of converted and ongoing conversion. I don't know if the list is complete but the page was last modified 2015-05-22, so it should be fairly up to date i guess.
There has been added in FreeBSD 11 but I am not sure how many of the commands have been converted.
[1] https://juniper.github.io/libxo/libxo-manual.html