Where can I find detailed growth strategies of successful startups in my niche?[I will not promote]

I’m researching a business idea in construction, and I’ve identified four companies that are already offering a similar service. While I believe I have a unique edge, I want to understand exactly how they grew—things like their customer acquisition strategies, marketing tactics, and monetization models. I’ve checked their websites, but I’m wondering if there are better ways to get deeper insights. Specifically: Are there tools or databases that break down startup growth strategies? How do experienced founders research competitors beyond the surface level? Any underrated sources (Reddit threads, case studies, interviews) that might help? I appreciate any guidance from those who’ve done this before!