“cofounder” isn't “what you're doing now”; it's “what you did 20 years ago” but it's important because people put weight on what the founders say and think. “[large] shareholder” is sort of a role, and often goes together with “member of the board”.

Bill Gates is probably a good example to look to. He also stayed on the board (as chair) and remained a large shareholder, and was looked up to as the cofounder. So I'd imagine “like Bill Gates but with less active interest and involvement”.