The 8 was last year’s LCD phone and the X was last year’s OLED phone (the first year it was offered.)
They also sell the 7, which was the phone from two years ago.
I agree it’s not worth thinking about unless you’re really into Apple news.
All three do Portrait mode, although XR uses its wide angle lens and computational photography for that, whereas both XSs use their two lenses (and the subtle shift between the two) with computational photography to make a bigger resolution depth map
I have a XS Max, but I'd say the XR is excellent (camera wise) and good enough for almost everyone. Let that not be your deciding factor