"I would like to create learning plans with set completion dates for individuals - not groups or cohorts"
Learning Plans (in Moodle 3.4) can be assigned to individual users or Groups, or Cohorts.
"Assign completed courses to users (as in a user completed a course or training intervention off-line and this needs to be put onto Moodle for record)"
OK, well you don't mean "assign courses" you mean "manually record" courses as complete.
Again, in Moodle you can do this using Course Completion...
...criteria can include meeting an activity's grade level or a manual checking "complete" by either the student and/or teacher
[Extract from https://docs.moodle.org/34/en/Course_completion]