Are they the same person? Or a previous incarnation before the Buddha was a human? Is there any Sutras that mentions/reference about this? (Pali Canon)
Not exactly from the Pali canon but hope it helps, since it contains comparable references to the Pali canon literature. (fyi. the Pali canon has suttas, Mahayana has Sutras)
The following dialogue provides a nice overview of the differences between them. It is an extract of the 2nd-century Maha-prajnaparamita-sastra, a key text of the Prajnaparamita literature (which was allegedly practiced by all past Buddhas and Bodhisattvas):
Furthermore, bhāga means glory (yaśas-) and vat indicates its possession. Thus this word means “the one who possesses glory”. No-one else has as much glory as the Buddha.
The noble cakravartin kings, Indra, Brahmā, the lokapālas, are inferior to the Buddha. What then could be said of ordinary men (pṛthagjana)? Why? The noble cakravartin kings are fettered by bonds (bandhanasaṃyukta): the Buddha has broken the bonds.
– The noble cakravartin kings are sunk in the mire of birth (jāti), old age (jarā), sickness (vyādhi) and death (maraṇa); the Buddha has transcended them.
– The noble cakravartin kings are enslaved (dāsa) by their passions (anunaya); the Buddha has eliminated them.
– The noble cakravartin kings dwell in the womb of the calamities of the human jungle (lokakāntāra); the Buddha has escaped from it.
– The noble cakravartin kings dwell in the shadows of ignorance (avidyāndhakāra); the Buddha lives in the supreme light.
– The noble cakravartin kings often reign over the four continents (caturdvīpaka); the Buddha reigns over countless universes (apramāṇalokadhātu).
– The cakravartin kings have mastery over wealth (pariṣkāravaśitā); the Buddha has mastery over mind (cetovāśita).
– The noble cakravartin kings covet heavenly bliss (devasukha); the Buddha covets nothing, having reached the well-being of the summit of existence (bhavāgrasukha).
The cakravartin kings seek their happiness from others; the Buddha rejoices in his own heart. This is why the Buddha surpasses (abhibhavati) the noble cakravartin kings.
He also surpasses all the other beings, Indra, Brahmā, the lokapālas who are even inferior to the noble cakravartin kings.
That should be enough right? The note says:
Compare the explanations of the Mahāniddesa, p. 142; Cullaniddesa, p. 466; Sumaṅgala, I, p. 33–34; Visuddhimagga, I, p. 210–212; Hôbôgirin, Bagabu, p. 46.
In the story (or tale or legend) of Gautama as a child, in the introduction to the Jataka Tales, it was prophesied that he might either become a Wheel-Turning Monarch, or become a Buddha -- see this answer for references.