Branching off multiple horizontal pipe/conduit runs?
Given that the conduit will be out from the wall owing to the Unistrut, I would put a curve on the end of the conduit, or an offset conduit.  Like these. 



The purple conduit curves up at the very end, and enters either an LB/LL/LR conduit body, or an EMT pull elbow.  Both have lids which allow access for pulling.  You never drag wire around this corner; you remove the lid and do two separate pulls.  

The LB or LL/LR conduit bodies put the long end into the box. An LB conduit body has a door on top where it might interfere with the second conduit run.  An LL or LR conduit body will have a door on the front for easier access at the expense of slightly harder pulling.    





The aqua conduit uses an EMT offset coupler to lift the EMT above the other conduits. Then it does an S-curve to get flush to the wall. 



Another way is to use a "tee" conduit body on the main conduit. 





Do this within 24" of the junction box.  You can't splice in a conduit body*, but you can run the wires around the T to the nearby junction box, and splice there.  If it's &lt;24", these extra wires in the main do not count toward conduit derate (310.15(B)(3)), but do count toward conduit fill (358.22, which you know about).



* For conduit bodies matching conduit reasonably sized for the wires therein.  If the conduit body is outlandishly large, you can do the same cubic-inch calculations you would do on a junction box, if it is labeled for cubic inches.  But it wastes the capacity of the connecting conduit if you do.