This article is chock full of useful info for all users: The real secrets of iOS and accessibility.

I quite often find myself wondering what I don’t know about what my phone can do, even though I feel as though I know it pretty well. Thank you for this…and showing me what I don’t know!

@crossingthethreshold I was quite astonished by a couple of things that I immediately implemented — eg per app text size changes.

@warner I'm still experimenting with settings, but Apple Mail to start with.

Two other great resources are Apple's iPhone User Guide and YouTube channel. All the "secrets" are mentioned there. 🤫 The official Tips app on iOS does a good job at surfacing lesser known features as well.
The fact that the iOS keyboard also works as a trackpad (for moving the insertion point when typing) is a feature I rely on that not everyone knows about.

@sod Thanks for those links. I need to train myself to use that 'trackpad' feature — I always end up fumbling about to move the cursor.