The original concept of Aragorn can be read in History of Middle-earth 6, where he was actually a Hobbit who wore wooden shoes, and was nicknamed "Trotter" rather than "Strider".
Tolkien agonized quite a bit over the identity of Trotter, and his plot notes (those which have been published) frequently enough contain the question: "who is Trotter?"
The emergence of Aragorn as a Man is covered in chapter 1 of History of Middle-earth 7, Gandalf's Delay, and I'll quote the note in full:
Trotter is a man of Elrond's race descendant of [struck out at once: Turin] the ancient men of the North, and one of Elrond's household. He was a hunter and wanderer. He became a friend of Bilbo. He knew Gandalf. He was intrigued by Bilbo's story, and found Gollum. When Gandalf went off on the last perilous quest - really to find out about Black Riders and whether the Dark Lord would attack the Shire - he [> Gandalf and Bilbo] arranged with Trotter (real name [other unfinished names struck out in the act of writing: Bara / Rho / Dam] Aragorn son of Aramir) to go towards the Shire and keep a lookout on the road from East (Gandalf was going South). He gives Aragorn a letter to Frodo. Aragorn pretends he is a
Ranger and hangs about Bree. (He also warns Tom Bombadil.)
Reason of wooden shoes - no need in this case because Aragorn is a man.
In other plot notes he was an Elf, and Tolkien even once reverted to him being a Hobbit before finally and definitively settling on him as a Man.
There's no evidence in any of the History of Middle-earth writings (nor in Tolkien's Letters) that Aragorn had been based on Bard. The story of the Fall of Númenor and the Last Alliance had actually already emerged before Tolkien started writing Lord of the Rings (see History of Middle-earth 5), and Aragorn was quite quickly identified as a descendent of Elendil. Again from Gandalf's Delay:
Trotter is a Ranger - descendant of Elendil? - he is known to Bilbo, and Gandalf. He has previously been to Mordor and been tormented (caught in Moria). Gandalf brought him back
towards borders of Shire in April. It was a message from Trotter that fetched Gandalf away in summer before Frodo left.
The name "Trotter" survived until quite late in the writing of Lord of the Rings, interestingly enough.
While there are certain similarities between the two characters of Aragorn and Bard, the indications are that whereas Bard was quite quickly achieved, Aragorn took substantially longer to develop and went through many false starts, and there's no reason to think that the similarities were intended to evoke the other character. These are all common-enough tropes, after all.
