It's a bit confusing. The pages describing Icelandair's pandemic policies (which ended earlier this year) are still live and do not make it clear that they are irrelevant for newly purchased tickets.

For a ticket purchased today, Saga Premium Flex and Economy Flex offer a full refund to your credit card. Saga Premium and Economy Standard are changeable with fee but your new flight must be within 1 year of the original date of purchase. Economy light, as you said, is not refundable or changeable at all.