They arestill powerful, but they are a very different creature. Shown below are a few pictures of Wyvern as compared to dragons. The first difference you'll notice is the legs; dragons have four legs, while Wyvern only have two. ... Wyverns have limited powers, and they are much smalle...
Do you have a source for Smaug being a miniature dragon compared to the dragons of the First Age? There’s not really any sources as Tolkien never addressed it all sources are just guesstimated, but in his books he does say that the magic and all things born of magic in the world ...