I think the answer to your question, if it is to be found anywhere, is likely to be in Canada rather than in Scotland.
There are 20 recorded baptisms of Angus M(a)cLeans between 1824 and 1828 in the Scottish indexes at
www.scotlandspeople.gov.uk, and probably several more whose baptism records, if they ever existed, have not survived. There could also be one or two in surviving records of dissenting religious denominations that have not become available to Scotland's People.
You can narrow down the field by noting the details from the baptism records and comparing them with the deaths index using the mothers' maiden surnames. But the deaths index starts in 1855, so you can't be sure that any of the remaining ones hadn't died or emigrated before 1855.
Without additional evidence there is no way of determining with certainty which one is yours.
A couple of things that may be helpful.
I could not find any of this Bute family in a census, which is what led me to wonder if they had emigrated.
You have confirmed that your Angus did emigrate, so the next question is, have you found him in any census in Canada?
What religion did he belong to?
Next, is there any evidence to suggest that Angus and Sarah might have known one another in Scotland? If so, it might be worth looking for Sarah in Scotland, in the hope that she might lead you to a clue about Angus.
Another clue could be in the names of their children. There is a tradition in Scotland of naming
- the first son after his father's father
- the first daughter after her mother's mother
- the second son after his mother's father
- the second daughter after her father's mother
- the third son after his father
- the third daughter after her mother
which isn't infallible, but can sometimes help.
And finally, do not trust anything you find online unless it's an original document. Especially don't trust online trees on Ancestry (or any other commercial web site). If someone tells you that Angus' father was John, you need to ask them for the evidence to prove it. "He's the only candidate who sort of fits" will not do, given the likely absence of records of other possible candidate.