I use a combination of Apple Notes and Apple Reminders. I have a project note, that includes a timeline, resources, and external links. I then share the note to Reminders, with each reminder being a task that needs to be completed, including a start date and deadline reminders.
I don’t use the subtask option in Reminders. It feels limited for me.
Depending on the size of the project, it might just be a few tasks/reminders. If it’s a larger project, I will create a separate List in Reminders.
Also, depending on the complexity of the project, I might link the project note to each task in Reminders. But usually it’s just the start and deadline tasks.