Discrepancy in iCloud and Google Photos storage for the same library

Recently i had to backup my 12 mini and transfer everything to my newly purchased 15 pro.

I have noticed that my icloud is almost full, when i was sure that i had plently of space left.

I have undo all changes and stick with the 12 mini until i find the solution but unfortunately status remains the same. (As i was not sure if by having two devices on the same icloud account, doubles up the storage and create duplicates)

I have no duplicate photos, nor any other shared albums etc.

Additionally, as an extra storage plan, i keep my iphone's photo also uploading (using its original size) to Google Photos (with paid subscription)

Still, i see 84 Gb of photos, while on Google i see almost the half, 43,7GB

Any other member experiencing the same issue? And if so, is there a solution?

[Re-Titled by Moderator]

Original Title: I have noticed that my icloud photos takes double the space than Google photos, for the same library