I've looked into several of these and have asked around others. For new startups that are remote, I 100% recommend going with a PEO provider (ex. JustWorks, Trinet, etc.). It may seem more expensive but you will save time and money in the long run by not having to do filings in each state you hire in. In fact, I would go as far as to say you should stick with a PEO until you're at ~50 or so employees. It's just not worth the burden to do otherwise. Gusto is quite good but they don't have PEO capabilities.