AA there are readily available data points to construct a "how many people to various forces shoot each year" league table - though not exactly the same as the number of rounds fired. Though one would hope that if shots are fired that someone (and the intended target at that!) would be hit.
I mentioned the warning shot idea as interesting as it runs entirely counter to the whole "reasonable force" setup we have in the UK (one that is apparently ECHR implied...). Firing a firearms is a use of lethal force, which is why you have
to shoot to stop rather than "shoot to disable" / "shoot the gun out of their hand". Quite what would happen if a warning shot went wrong and hit an unintended target I dread to think - a murder charge I'd imagine. Though Germany presumably has different laws that allow such things.
As to the "best practice being left of centre"... Methinks that is your political view in general
That would be where the UK lies, given a ridiculously low number of people per capita are shot by the police. Which leads to a rather ridiculous situation where every firearms incident is investigated as if the people wielding the firearms are German reservists or rural American deputies that can't be trusted to not be incompetent or corrupt. It leaves no middle ground between unarmed cops and officers so tooled up they give rise to "paramilitary" claims.
What I would be interested in is the amount of knife crime on cops in other, armed, European countries v the mainland UK and Republic of Ireland which are routinely unarmed.
PS. There is a massive problem anyway. Rounds discharged or people shot isn't just a comparison of "best practice" of firearms policing, or indeed policing in general. It is far more likely to be reflective of the type of crime and criminal prevalent in that country.