I have this small starfish pendant and love it! It's a nice size, leaning towards medium, and very wearable for everyday use. Your post reminded me of a pic I posted earlier in the thread (see below). May be useful for you, as it shows several of your pendants along with the small Sea Star. So helpful, I think, to see pieces together to be able to compare sizes. Seems like it would be a nice addition to your collection!
I agree, though, there are so many beautiful TSC options, can be hard to choose! I tend to have a loose wish list of things I'd like to add (currently, mine are all TSC as this brand captures my heart, most). In my case my list has been categories along the lines of: large amulet, long chain, medium pendant, fine, short chain, coordinating earrings, etc... I tend to like to fill holes in my collection because I enjoy wearing her pieces frequently, and it gives me more opportunities to wear them.
Let us know what you decide!