NiceHash is a great service that I’ve utilized over the years and it’s what I always tell newcomers to check out that want to get into mining Bitcoin. It’s the simplest way to earn some BTC with your home computer. I don’t know how serious it is for asic mining compared to competitors, but as far as being a reliable service, NiceHash is legit.
Basically, ASICs are designed for one algorithm and NiceHash will not be very useful, because it is easier to mine for a large pool without registrations.
I have tested this service in my 9 years of mining, but I was taught to use pools from the very beginning, and I try to avoid additional intermediaries in mining.