I would be curious though if the more expensive and involved driving license in many European countries results in better outcomes though. Wouldn't be surprised if the main factor is practice over everything else.
European driving licenses are expensive because they require more practice. You pay for the practice hours. The tests themselves are much cheaper.
It doesn't. UK road fatalities are very low compared to mainland Europe and it doesn't matter much whether your divisor for that stat is number of vehicles or number of miles driven. It's arguable how much of that is down to the driving test and how much down to other factors like rules, rule following behavior, etc etc - but I think at least some of it is.