Many moons ago, a POS control tower would give you the distance to any other POS tower in the Corp in light years.
This feature was used by an enterprising group of players in an attempt to “map” wormhole space soon after their introduction into the game.
By anchoring towers at the far reaches of the k-space map, then placing a tower in each wormhole they encountered they could triangulate the position of the wormhole system relative to known space.
The project was cancelled when ccp, for reasons never fully enunciated, removed that feature from control towers.
Speculation is that the full Anoikis map is basically a carbon copy of the k-space map, shifted a few hundred light years.
But yes, j-space has constellations and regions. The theory on site respawn mechanics is that a site run in j- space will respawn in another j-space system in the same region.
Please note the theory on site respawn mechanics is just the best guess of wormholers over the years. It’s never been confirmed by ccp that this is how site respawn mechanics actually works.