Kauai and Oahu traffic?

My husband and I will be staying in Kapa'a next week and Waikiki the week after. We'll have car access for both and we're planning on doing a lot of driving to explore local spots and hiking trails.

I'm trying to get a sense of what to expect in terms of traffic? We're from NYC and used to driving in Brooklyn & Queens where "normal traffic" means it takes 40 minutes to go 10 miles. Is Kauai/Oahu traffic generally worse compared to that? I'm not stressed because we only have 2 tours booked where we need to arrive at a certain time, mostly just curious about what to expect since the majority of our plans will be on our own time.