Question about snipcart JavaScript SDK, difference, benefit and advantages

What’s the difference between snipcart js SDK and regular implementation of snipcart?
Does the snipcart JS SDK is like API only snipcart?
And does the JS SDK also comes with snipcart default styling that needs overriding?
And it’s well maintained as regular implementation?

Anyone that can help with this? I think i saw on snipcart roadmap