Translation:Vietnam has many mythologies and legends.
My understanding of the difference between myths and legends in english is that a myth involves gods, demigod and the supernatural (e.g. Zeus, Hercules and Werewolfs) while legends only involve humans and have no magic / supernatural side (e.g. Lady Godiva).
I wonder if it's the same for thần thoại and truyền thuyết in Vietnamese?
Mythologies are categories of myths, e. g., Greek mythology includes many myths. Unless Vietnam has many different mythological systems, "Myths" is the right word here.