E: There isn't a wrong or right time to approach an investor. My personal preference is early-stage, because it’s a chance to meet the founders from the very beginning, build a solid relationship, and grow and progress with the startup. In this case, the startup progresses and starts fundraising, and the pace is much faster.
Still, I would mostly suggest that founders reach out only when they’re ready with a proper pitch deck, and are actively fundraising. Sometimes founders try cold reach outs, like through email or LinkedIn, just to network and meet investors. If their pitch deck isn’t ready, or their startup isn’t actually fundraising, this may not be the best strategy as investors may lose interest overtime, considering how dynamic the entire sector is.