I’m a big lover of the ecosystem and a heavy Emacs, but after several attempts I couldn’t get into Org mode: (1) it’s too complex and full featured, while my loose mind requires a strict and minimalistic system to be productive; (2) mobile support is quite lacking — yes, there’re beorg and Mobileorg, but they don’t do it for me for one reason or another.

So I’ve a custom GTD-like system build using iOS reminders, .md files, and a couple of scripts.

Yes, or Org mode can be quite complex if you let it be. I mostly only use the same features as markdown supports: headings and code fences.

For mobile (Android) I use Orgro.