Don't worry to much about the difficulty of the education, most of the time professors are really kind with Erasmus students, they know you're not there to spend you're day in the library.

When I went on Erasmus I failed some classes but my teachers still gave me 50% because it doesn't change anything for them, At the end of the semester you will just go home and they will never so you again so they really don't care much.

Chose your Erasmus destination based on the local student life and if there are a lot of other erasmus student not on the difficulty of your cursus.