In my opinion Belle, Pocahontas, Rapunzel and Merida are very romantic, despite finding their significant other isn't their biggest dream. I also consider myself to be extremely romantic person and I've never dreamt about getting a love interest or marriage.

Tiana is the least romantic DP IMO but not only because of her initial uninterest in marriage.

Yeah, how do you define Merida as romantic if she isn't interested in love/marriage ATM?
I suppose you could classify romantic as in an idealized view of reality but that's not how the term is usually posed on here.
Pocahontas and Belle can still be very romantic without finding love being their biggest dream, but it doesn't make them the most romantic DP to me
IMO, at least not in the romance/love sense.

"exciting and mysterious and having a strong effect on your emotions"(c) dictionary - Merida fits this description IMO and so do I.

"not practical and having a lot of ideas that are not related to real life"(c) dictionary again.

Sure, it's just ONE of the dictionaries and you can have your opinion.

not necessarily. One could have ideas about love or fantasize about certain kind of life to be romantic by heart.

When referring to the princesses, I generally take it to mean finding love.