Fennekin is easily my favourite, it's just so aesthetically pleasing. Froakie has its charms too. I'm really not feeling Chespin though, it just looks like the basic route 2 encounter rodent. Of course all this could easily change with what the evolutions bring! The final form is what is really important.
As for secondary types, I'm hoping for Fennekin's evolutions to be part psychic. Froakie I could see becoming poison maybe?