Really depends on where you are in Europe. Out here in the boonies of Portugal, it’s excellent if you’re driving a 4x4 pickup truck, which is the only vehicle of mine I use it with, as it picks very direct routes, which often involve ridiculously steep muddy dirt tracks, very narrow bridges, and generally just very underused farm tracks.
I tried using it in Bosnia, once, and it decided to use an abandoned airfield landing strip as a shortcut. Wild stuff.
This is my exact experience, but with Google Maps. Constantly suggesting gravel (or worse) side roads instead of highways and hallucinating multiple turn lanes etc on a country road about 1 car wide. It's been a few years, but I still remember the time I was in Berlin and buses didn't run due to bad weather, but I had a flight to catch so I had to walk to the Tegel airport and the route Google maps recommended ended up being quite an adventure, having to crawl through a hole in a linked fence on an unlit dead-end road next to the airport.
No, and as far as I know, they don't say. But a lot of their not-direct-from-OSM map data comes from TomTom, which also ingests OSM. There's a lot of OSM in Apple Maps, as there is in most other non-Googly mapping apps.
Apple Maps is absolutely very late to the game when it comes to road closures. Google Maps somehow always knows which roads are closed, even if for a few minutes.
Apple Maps does have the ability to make the same reports, but its super buried so I doubt many people even know its possible, let alone where to go to do it.
I tried using it in Bosnia, once, and it decided to use an abandoned airfield landing strip as a shortcut. Wild stuff.