My telecovers often touch each other, so that's about as close as you can get. But for easy of working I prefer more butt-room b between the hives. I doubt the bees care much. In Europe, it's not uncommon for some hive setups to share common walls on a specially-built trailer.
All my entrances face the same way, BTW, whether centered or reduced with the reducer in place.
Sometimes I speculate that my unusually calm yard benefits, collectively, from appearing to strangers outside the yard as being a single really, really, big colony not worth messin' with just to steal a bit of honey. I have mixed-sizes of hives within the yard (from a nuc, to three-deep wintered-over Big Girls) though. I also protect most entrances nearly all the time with robbing screens, which are identical in design. A quiet. unfussed, "happy" yard is one of my main goals.
Nancy