It was different per country. In the UK, tape was quite dominant, but at least here in Austria, the 1541 was far more common. AFAIK it was the same in Germany.
Indeed. I think in the US basically everyone had a disk drive whereas in the UK almost nobody had one. In The Netherlands and Germany they were quite common, as well.
Not sure if the nordics were a mixed bag or not, as i don't recall anyone using tape for their C64 (but a few had UK computers, the Amstrad CPC in particular).
My impression is that the clear majority of the Nordic C64 users had a datasette and tapes.
My cousins were part of a cracking crew on C64. Almost all of the (hundreds of) games I had were ISEPIC'd and 5-10 to a floppy disk.
It took me years to realize that was pronounced "ice pick" and not "i-sep-ick". I didn't know any better.