The answer in most situations is going to be yes. One of the virtues of an LLC is its simplicity. Once you choose to form your business as a corporation (and then an S Corporation), or to have your LLC elect to be taxed as an S Corporation, costs for tax returns, payroll, corporate state compliance paperwork, and other accounting items get triggered. You'll need to balance the benefits of an S Corporation against the ease of use that comes with an LLC.
No. You may get background checked as a vendor, even if you put your business in a corporation. But incorporating does not require any background checking.
In terms of capital (i.e., cash money), it depends on your business; one common rule of thumb is 3 months’ worth of cash to run the business. If you mean compliance, you’ll need annual minutes and, in California, an annual filing with the Secretary of State. You’ll also need to memorialize extraordinary transactions, like leases and financings, in your corporate records. Without minutes and/or consents, you could expose the shareholders personally to liability.
The answer to this is similar to the answer for the same question for corporations. However, with LLCs, unless the members require it in their operating agreement, there’s no requirement for meetings and consents, unless the written consents are required by a third party, like a bank. This is the reason some folks try to use LLCs instead of corporations.