Thanks for reaching out! You can submit to OSF Registries at any point. There aren't any really hard guidelines because we want to encourage research transparency, credibility, and rigor. That said, our registration process has several templates that you can use for your submission. For the systematic review, you may want to consider our OSF Preregistration template. This template is our more rigorous one and challenges researchers to think through different aspects of their research they may not have considered. Alternatively, you can also use our Open-End Preregistration, where you can upload a document that customized for your discipline and organization and register that way. You will find both of the templates and more on
this OSF Project.