I have been reading on my phone before falling asleep for many years now. I use an app with amoled black background and yellowish peach font colour. I haven’t felt any eye strain or difficulty with sleep.

For me, yes. I notice that whenever I’m reading on my phone (night mode, blue light filter, lowest light setting), I will stay awake longer, my eyes strain, it takes me longer to fall asleep. When using my kobo (not backlit, but still lit - it has those leds all around the screen that light it up from above!!), it’s like I was reading a paper book, except I can read in a dark room without any strain to my eyes whatsoever, and I can take on any position without having to adjust the light source!!! An absolute game-changer in terms of comfort. In fact, I think my eye strain is even lower with the e-ink reader compared to regular paper indoors, because I have a better light source no matter where I sit in my room.

I think it depends on if you feel it’s keeping you up or causing eye strain. I find a backlit Kindle has a decent amount of brightness and is easy on the eyes.

Using an iPhone I’d be more worried about distractions than anything else

The truth is that using a backlit screen before bed will affect everyone differently. Try both and see which works better for you.

Another vote for a backlit e-reader. Much easier on my eyes in a dark room than the dark mode on my phone.