After trying every kind of fancy task management and note taking system from org-mode to Obsidian to Logseq, I now use a .rtfd (.rtf + images) on iCloud to act as a note-taking system / todo-list. I would have used pen and paper but I need to paste screenshots and URLs.
There's an iOS app called RTF Write for 99c. Now I always have my notes, tasks, and shopping, and above all, it's so simple and quick.