At my last company, we built quite a large waitlist (25-100k…can’t remember the exact size). We found that while it was good for hype and PR, converting people wasn’t that easy because people had often forgotten about what we were by the time that we launched.
I think it can work if you actually onboard people from the waitlist pretty quickly.
Think it really depends on how long you plan to launch afterward and why you’re doing it. Waitlists are great if you want to tinker on the product with a small number of users, less great if you’re not ready to launch and just doing it to get emails.
Built it ourselves, we basically had X amounts of groups and you needed Y invites to move up groups, we invited the top referrers first. There were also some prefilled tweets that people could pick from.
I’d onboard the top group super early and get them hyper-engaged with the product (think Superhuman) and allow them to invite their friends to skip the list. Also do more A/B testing with messaging and build a better product before onboarding people. We were all pretty green so it wasn’t the best execution!