I can only answer briefly, based on RAF aircrew accounts, so my answer won't be comprehensive, but it may give you some idea of how the crews felt about it.

For the RAF aircrews, they didn't seek to kill civilians etc. Attacks were carried out against targets of military value (Industrial areas and rail yards, etc.)

When the RAF went to places like France to attack targets, crews would generally try to be more accurate in their bombing attacks. Many crews weren't comfortable with raids on German targets where they could see fired burning for up to 100 miles away on the return trip. (However, this view wasn't universal.)

In terms of civilian casualties, they were unavoidable given the accuracy of bombing at the time and civilians died, with RAF raids on Caen just after D-Day claiming as many as 5000 French lives.