Moved from Australia and need help setting up my Tax stuff for my Sole Trader Business

Hi there!

I had moved here from the land down under, got my Work Authorization and SSN sorted and in hand. I am ready to set up my business and I am absolutely clueless how tax works here form a sole trader standpoint. (For context my business is done from home on my computer, no physical locations and such.)

I am in the state of NY.

In Australia it was a one and done deal, only paying tax to the Fed gov. It seems here in the United States you need to pay the State and Fed gov for tax?

Is it better to make my business a LLC or Sole Proprietorship?

Am I required to pay GST/ set it up for my small business?

Do I need to charge clients/ customers GST on each sale even as a small biz?

I want to be as efficient as possible to be able to save on tax in the best possible way, basically to avoid being over taxed by doing something wrong/ not being in the know of something.

Is the gov more flexible on what you can claim as a deduction?

I was told by my accountant in Australia that any tax I pay here in the US can be used as a credit for my Australian tax (so I don't get double taxed)

Any pointers is greatly appreciated! Thank you :)