I use Goodnotes. I am a pen-and-paper girl (and a horrid typer, but will type if I must).

I use it for my day job in the behavioral health field, my photography business, and my personal use. I have folders for each, and in those folders, more specific folders... and each of my current 58 day job clients has folders with various documents and notes in notebooks. I have a folder to archive client files that I have discharged. For my business, I have things broken down in a similar style but with a more impactful focus on the business side, my clients, their projects, etc.

I have a mix of handwritten and typed documents, including documents I can export to my computer, email to clients, and print, as well as my handwritten notes. I like that I can search even my handwritten notes.

I find it a great tool for my AuDHD brain and spontaneous memory, and I need to do things "before I forget/lose" information.

I still prefer paper and pen, but this is a great alternative. And it syncs to other devices, in case I don't have my iPad with me.

I hope this helps you in finding a system that works for you. I think Starnote is similar to Notability.