Well, that's a tough choice. Novels offer more depth in character development and inner thoughts. Comics, on the other hand, rely heavily on visuals to convey the story quickly. Consider which form you feel more passionate about and have the ability to excel in.
Sure, you can give it a try. While Buffer isn't specifically designed for story creation, you can utilize its basic text editing capabilities to start crafting your tales. Just keep in mind that for more elaborate and polished story writing, you might want to look into dedicated writing software.