I always curious what make a knife "Bowie" ? Does it really need to be clip point? can a drop point or harpoon or persian style qualified as Bowie knife? Does a clip point kitchen knife count as bowie?
The first "bowie", according to Rezin Bowie, was a knife that he had made by blacksmith Jesse Cliffe from an old file. Rezin's description of that knife was printed numerous times in old newspapers from a letter that he sent. It had a 9 1/4 inch blade and had a straight back.
Other than that, pretty much anything and everything can be called a bowie knife, as the way people used the term developed over the years and decades. I think most people would reserve the term to a knife that is (1) large, at least a 9 inch blade; (2) has a full guard; and (3) has a clip point.
In my book, a bowie knife is any large knife that is made for fighting or self defense as one of its primary duties, even if it doesn't have a guard or a clip point. The modern bowie has developed without a guard or clip point. Check out the new Jack Hammer 10 by Busse Combat. That is certainly a bowie knife, in my opinion. TOPS has many large knives without guards or clip points that are also bowies.
To answer the OP's questions:
Clip point necessary? No.
Drop point, harpoon, persian style? Yes, certainly can be. It's in the eye of the beholder.
Clip point kitchen knife? If the maker went to the trouble of making a clip point (a classic bowie hallmark) on a kitchen knife, I'd say that's definitely a bowie, especially if it's at least a 9 inch blade.