I found the source of this issue!
since it wasn't present on my other PC, I compared all of the settings and the only difference was on the "Taskbar button combining"
So, if you choose "Never combine taskbar buttons", the icons are not aligned (probably a consequence of the display of the text, text that you can't see if your taskbar is too small)

Then, if you chose "Walsays combine taskbar buttons", everything is centered (except for the sound button, but since there isn't any problem with the hover or the Internet icon, which is in the same "space", I guess it's more an icon issue than a setting issue, there is pribably some void on the right of the icon)

Anyway, thanks for the help!