I have not seen anything anywhere (I've googled) that really explains the the
pros and cons of having multiple profiles vs one with multiple email
accounts. From what I've read, I don't know if either will work well for me.

I have three email accounts, all of which I need to monitor simultaneously.
I do not want to have to remember to change my "from" or "reply-to" when I
respond to mails sent to any of those accounts. Nor do I want to have to
change these when I write an email, wanting it to have it come from a
specific address. It does not seem I can have multiple instances of Outlook
open with alternate profiles. So, what is the best way to achieve what I want
to do? What are the pros and cons of the various ways of setting it up?