hi, Kyla. I have Tagetes lucida (also called Mexican Mint Marigold). I grew it from seed this past spring. It was very easy to grow. It does not give any indication of being invasive but apparently does produce seed. I'd be very happy to share some seeds with you! Plus, I think the seed packets were easy to find at local nurseries.
I totally agree about not buying seed packets (or plants) from companies/stores that don't provide clear botanical names.
PS--I look forward to seeing photos of your tarragon plant, Kyla!