OP, if you can block something between $1M for 5 years, I will seriously recommend EB5 as the most well known option. All the Chinese millionaires are immigrating using that. I know it works and is not super complicated. It may even be possible to do it with only $500k invested if that investment is certified to be helping a distressed area.
If you can swing this, then you will only need an immigration lawyer (and not a very specialized CPA + immigration lawyer).
For immigration lawyers, google gives me this tool to search for a lawyer :
https://www.ailalawyer.com/AILA the biggest such immigration lawyer's association in US (again, info given to me by Google).
I don't know how to tell who is good and who is not. I would recommend that you find a few of them and talk to them how they would tackle your case, and select based on them. Most lawyers should offer a free initial consult (it's common here in US in the other fields, so it should be common in immigration law as well).
If you go corporation -> sponsor yourself, then I suspect the total cost for the CPA + immigration lawyer will likely be much more than the EB5 approach. You need to balance that cost against the opportunity cost of blocking 1M on a suboptimal investment that the lawyer directs you to :-(.
It's a bloody friggin' racket!! The bloody US government should really wise up and roll out red carpets for people who wants to invest in the country.