Which filter should I use to achieve this effect?
I have applied the dry brush effect on my watercolor-like image. But cannot get the smooth edges like the one above.
You're in the wrong application. Not that it can't be created in Photoshop but that was most likely created in a Vector Graphics Application. If you have the Creative Cloud then use Adobe Illustrator and either start from scratch or could just load your progress so far and
Image Trace it:
If you don't have Creative Cloud then Inkscape has some auto trace feature as well but I've never used it to know how well it works.