The question of how much (if any) backbeat is interesting. From what I can tell in the time I've spent playing this music, it's highly variable. More of a personal preference or group decision in a session than a fixed rule, like the degree of dotted feel to use for a hornpipe. Some tunes seem to want it more than others.
Saxomophone wrote:
Mostly I’ve been learning by playing along with recordings but I’ve started working out of a book. In the book it covers accenting the backbeat or upbeat or last note in a group of triplets. It says that the backbeat should be emphasized above notes that would normally get a melodic accent.
I disagree with the book's advice that "the backbeat should be emphasized above notes that would normally get a melodic accent." Sometimes what happens is the backers in a session will be using a backbeat emphasis while the melody players are using a "melody pulse" that floats on top, and the emphasized notes may not always land on the 2 and the 4.
Here's an example of that, a video clip of a pub session with Martin Hayes sitting in. Notice how the emphasized pulse in the melody line often hits beats other than the 2 and 4, while there is still something of an overall backbeat feel in the tune:
https://www.youtube.com/watch?v=EelRwZM-MEw