How does Voltaire address the Enlightenment notions of rationalism, skepticism and romanticism in Candide?

All three of these schools of thought are definitely portrayed in Voltaire's classic satire Candide.
Voltaire shows these schools in different ways, however.
You can see the young Candide as an embodiment of Romanticism. He is also romantic. That is to say, he is romantic in his love for Cunegonde. He is also a very Romantic figure. He is the sort of innocent Rousseau celebrated in his work, and goes out to meet the world in a spirit of trust, even love.
Dr. Pangloss is very much a figure of rationalism. Again, he embodies rationalism, much as Candide does Romanticism. He has a rational reason and a theory for everything. All that happens is explained, even explained away, and he meets the world with his theories first, his emotions a distant second.  
More than one reader has seen Pangloss as a satire on the philosopher Leibniz. You can see what happens to Candide, and what happens to Pangloss and his theories, as Voltaire's position, which you could call a deep, even profound, skepticism. This is reinforced by the way that no system is allowed to stand unchallenged, and no public explanation of the way the world works is allowed to go unskewered.
Candide may be a Romantic figure (and again, a romantic one), and Dr. Pangloss may celebrate rationalism, but Voltaire can be seen in the workings of the plot and the novel's events, and his world view is very skeptical.
https://plato.stanford.edu/entries/leibniz-evil/