Should I make a backup of OSX before bootcamping Windows 10
I would strongly recommend making a backup before setting up Boot Camp. Setting up Boot Camp involves repartitioning the disk into an OS X partition and a partition for Windows, but OS X doesn't know how to format the Windows partition into NTFS. So, it formats the Windows-to-be partition in the FAT32 format, and expects you to use the Windows installer for reformat it into NTFS. If you don't do this quite right, the Windows installer may reformat the OS X partition as well, causing complete data loss.

Thus, it's much safer if you have a full backup. Just in case.