LPDDR—Low power dual data rate
The latest technology used in random access memory (RAM).
LPDDR4/4X/5 — where 4/4X/5 represents a generation.
LPDDR4X is latest for mid-range smartphones.
And LPDDR5 is used in flagship phones.
In OnePlus 9 Pro.
Now here comes to UFS: "UFS" – Universal Flash
This is the latest technology used in read-only memory (ROM).
There is also UFS 2.1/2.2/3.1.
The same situation is also with LPDDR, i.e. UFS2.1/2.2 is used for mid-range phones
WHILE UFS3.1 IS USED FOR FLAGSHIP PHONES.
It's also used in the OnePlus 9 Pro.