A good way to examine would be to look at Louisiana. Some elements of French law were maintained, and some diversity in how it does its elections has been permitted over time. Now, Quebec would have never come under the Code Napoleon, so it might be different.
It would be open to settlement, but keep in mind, had it gone pro-American after 1783, it would have been because the Protestant Anglos who backed the invasion in 1775 would be in an ascendant position, and they'd likely dominate the distribution of land, just as the non-Quakers dominated land distribution in Pennsylvania after the war and sidelined the Quaker faction to a large degree.
As for boundaries, well, the British would likely have little interest in Ohio country or Upper Canada if they did not have Quebec, as these areas would be cut off. They'd probably keep control of the Maritimes and Halifax, where the Loyalists would go.
Had it somehow gone American after 1815 instead (ASB, I know, but bear with me), than it would be a completely different situation, as the United Empire Loyalists and others would have to be taken into account.
Its possible that powerful landholders push for some kind of return or guarantee of seigneurial rights, which would put Congress in a conundrum, as they'd naturally resent that from an ideological perspective but they were allied with Ancien France, who would likely push for that, if not control of Quebec in exchange for war help.