I was there last year in early November and was the designated driver. I don’t mind driving on the left at all (with an automatic) but it was simply a lot harder to see after dark. Add that to the narrower unfamiliar roads (and in that area you will find a lot of narrower roads) and it was far more than my level of risk tolerance. For me, the M roads were fine, as well as some of the N roads. Nothing smaller. And I did a harrowing drive Cork to Killarney on an N road after dark I would never repeat. I am only talking about driving after dark, though, not during the day. In the daylight, I actually enjoyed the driving on roads of all sizes.