Create as many projects as you want without any limits. You can invite all the members of the project who have something to do with the project. Each project is accessable only by members of the projects.
Add tasks to your todo list online. Every project has its own activity boards, See list of members who have access to the projects and you can also connect a project with some other data, like notes, lead, contact or sheet.
Categorize your tasks into different task groups