In the World After COVID, this will become more relevant when "anything you book on points is refundable" policies end, as different fare classes will have different rules for changes, etc., but one thing that has stood out for many of us is the new addition of Latitude awards, which allow you to book a flight and confirm an eUpgrade months in advance, often for substantially less than the cost of a Business Lowest award.

More details on that here, at a blog to which I contribute: https://www.flyermiles.ca/post/the-latitude-trick