Isn't
Tegan strictly feminine? It seems like that to me and says so on this site, kind of like
Rhiannon or
Tamsin. It also reminds me of
Megan.
I think
Teagan is the unisex one, but it has a different etymology. But I guess they sound the same so I see where you're coming from.
To me
Tegan has something very feminine about it, I get a similar image as I do from
Rhiannon. I think of a queen on a horse :)