Yes. Every where you run “sls …” has to have “sls login” done or an environment set. You can have unlimited users, even in the free tier as I understand it.
Our problem is you can’t migrate a single project/client from v3 to v4, it’s all or nothing : Serverless 3 & 4 together
At some point Serverless are going to update their Chocolatey package from v3 to v4 and break everything.