Hey, thanks for the question. Is what you need a community forum like these Webflow forums? In that case, you don’t even need to build your own solution. Just use something like Discourse (which powers this website).
With this option, you could use Webflow to build a pretty landing page and meet your requirements as a graphic designer, then from there simply link to your instance of Discourse. This can handle all the user registrations, logins, password resets etc.
Otherwise long term yes, Keyfold will probably be able to solve your problem. Unfortunately it won’t be able to within 3 weeks 
Having said this, I do need to identify some alpha testers so if you’re keen just send me a message.
Cheers,
Jason