For camera capability, the order of quality goes:
L series - most basic model
10 series - mid range with decent camera and phone tech, with a few cost savings around here and there
1/5 series the range with best tech and best camera tech
Xa series is pretty much gone now, everything changing at Sony to bring mobile in-line with the alpha camera department, so XA bacame 10, XZ became 1 (&5) and L became... Well, it's still L because it's the entry model and is ok on its own like that.
Depending on which Sony phones you've had before, could alter my advice for which handset, but a good rule of thumb is:
If you like the basic, and have used L, M series, go with L4
If you've had XA and like the general use with a few decent camera specs, go with the 10 (or 10 mark ii, which should be appearing soon)
If you had Z, XZ Or other flagships, and like the best features and fastest specs, you should go with 1 series if you like larger phones, or 5 series if you like them regular size.
Of course the 1 series has the 4k oled screen but for most FHD+ is more than enough..
As well as 10 mark ii, 1 mark ii is also due soon.