Coral Beach at Carraroe, west of Galway:

Biggest difference is that Ireland isn’t as wild and unoccupied as Scotland. You feel like you’re in the middle of nowhere, round the next bend and you’re at a village or a pub or some other small population centre or tourist attraction. The scenery is the draw rather than the feeling of being miles from anyone.
On the north side of the Ring of Kerry:

The roads are all wide enough for two cars to pass. Most have a white line down the middle. But this does mean there are even full sized coaches using them. There would be some nice driving roads but it’s generally a much more busy part of the world.
The Shannon ferry crossing from Killimer to Tarbert:

There are some lovely places and views; the road for a mile or two south of the ferry at Tarbert runs alongside the water and the views are distractingly beautiful. But I expected the ferry to be an idyllic little crossing and in reality had to drive to a very commercial looking terminal at Killer straight after having passed what looks like a fairly new nuclear power station. It feels totally different to doing the NC500. You won’t struggle to find a petrol station, probably even EV charging.
Overall the two routes are not at all similar in terms of either the roads or the general feel. I did love the Ring of Kerry although my wife complained it felt like we’d been driving all day. I really liked some of the towns and villages we stopped in or passed through. We particularly liked The Burren. We laughed about the tourist attractions being pretty much all like Father Ted’s Holy Stone of Clonrichert or St Kevin’s Stump. It rained quite a lot. We had a lovely time. But next time will be Scotland again.