and a delay depending if the symbol is a letter or a space.

That's how I did in Unity! Though working with visible characters in Unity is a nightmare itself.

I made a custom effect that affects only alpha and then ran it through the string like a caret.

Have to add though that 0.3s transition from pitch black to bright white is better than instant flip. I'm photosensitive (mildly no seizures) and if there is a little tiny transition I don't feel like it's a stroboscope (sample size just me here.)

Off my hand use cases:
Cut TO and FROM
Appear/disappear on screen.
Crossfade for animations
Time between frames on flipbook animations

I dunno, maybe somebody finds it useful.