I don't think the deep sectarian divide in Northern Ireland can be dismissed as a 'detail'. It makes the situation over there fundamentally different from that in Scotland.
For Scotland you can pretty much talk about the Scottish people as a more or less unitary group. The devolution referendum was decided based on debate and argument. Sure there was a strong nationalist component of it, but that didn't completely override all other factors. It was just one of many important factors, and you can't argue that someone to voted Yes or No is clearly more or less Scottish then the other. Factors other than national identity play important roles. For example if the UK votes to leave the EU, that will likely play a decisive role in many Scots switching to prefer independence so they can stay in the EU.
When talking about the situation in Northern Ireland, you can't really talk about 'The Irish' as a group the way you do in your post. A vote on devolution there would have nothing to do with debate or weighing of pros and cons. Staying in the EU or not would be a footnote. Any such vote would be a straight down the line sectarian census.