@halfbyte Two things: I have the same issue with HiDPI, but I just resorted to running my screen at 1920x1080 instead and skip HiDPI completely. My eyes are neither sore nor strained from it and it still works as expected.
For online/offline backup I can recommend Deja Dup, which is almost as convenient as Time Machine: https://launchpad.net/deja-dup