Our idea achieving same results and it's basically the same thing, but it's slightly different system used and the way is installed. On the top of that, I see other companies doing same thing, how can I check if they pay some kind of royalties to the owner of the patents, or they just do something slightly different?
If you sell a product in the US and infringe on a US patent, you indeed may be sued by the patent's owner. It doesn't matter where the product is manufactured. That said, you have to carefully read the specific patent's claims to know whether or not your product infringes. A patent attorney is your best bet to do a "freedom to operate" analysis. As for whether some company is paying royalties on a patent, I doubt there is a way of figuring that out unless the company itself makes the information public. However, I could be wrong.