LLC statutes in many states permit the operating agreement to modify or eliminate fiduciary duties, within limits. The result is that two companies with identical structures can owe entirely different obligations.
What can usually be modified. The duty of loyalty may be restricted by identifying specified types or categories of activities that do not violate it, if not manifestly unreasonable. The duty of care may be limited, short of gross negligence or intentional misconduct in most statutes.
What generally cannot. The implied covenant of good faith and fair dealing is typically non-waivable, though the agreement may prescribe standards for measuring performance. Bad faith violations of law and knowing misconduct are usually protected.
Express waivers of competition are common where members have other businesses, and are frequently the reason a member is free to compete with the company that would otherwise be a clear breach.
The drafting consequence. A member relying on default fiduciary protections that the agreement has displaced has no claim. Any investor in an LLC should read the duties article before the economics article, because the economics are enforced through the duties.
Where duties are eliminated, the implied covenant becomes the whole of the protection, and courts apply it narrowly — filling gaps the parties would obviously have filled, not rewriting a bargain that turned out badly.