I only backup .julia/dev. Because that’s where files reside that I edited. I think of all the other folders in .julia as just caches that Julia can quickly recreate from scratch when you instantiate your projects.
In fact I define the environment variable JULIA_PKG_DEVDIR to point to a location that is backed up, and I point JULIA_DEPOT_PATH and JULIAUP_DEPOT_PATH to a location that is not.