In and out within 30 days

is free with your H-1B. Many people have done this. Just don't submit your I-94 at the border and take all you H1-B application package with you.

To enter from a third country, say, China, you will still need a valid visa, which means you will have to apply for a visa in a US consolate, either in Canada, or China.

If you are lucky to get a multiple entry Visa, then you are pretty much free.