wire lengh question with copper bus bar for 3 banks of batts rolls L16 445ah.

Bus Bars have resistance too... So, ideally, for example:

Left side of your drawing--Bus bar connections
Chargers +
batt 1
batt 2
batt 3
Inverter/loads +

Right side of drawing--Bus bar connections
Inverter/loads
batt 1
batt 2
batt 3
Chargers -

That way, the "electron paths" are all equal. As you have drawn, the chargers and inverters "in the middle" means batt 2 has the shortest paths and the lowest resistance, and battt 1/batt 3 have longer total path lengths and higher resistance (comparatively speaking) and those batteries may/will share a bit less of the charge/load currents.

Yes--Keeping +/- pairs of cables together is the ideal. For example, if the +/- cables are not together and run as a "loop"--You have a nice loop antenna and the wire runs become more susceptible to lightning energy and a better transmitter of electrical noise from your chargers/inverters/loads.

For "different circuits" (say DC and AC circuits) they should not run in parallel/same conduit. You want separate runs to avoid cross talk between the circuits and if they must cross--Cross at right angles to each other.

You did not ask--But another issue is when running wires into metal boxes (such as a breaker panel). For AC wiring, the Hots and Returns (L1, L2, Neutral) main power/branch circuits... Each "set" of AC power leads must enter and exit the "metal" boxes through the same hole/knockout.

If you run an AC circuit of  L1 (black or red "hot" wire) through one knockout and return (neutral white wire) through a second knockout--That sets up a "transformer" situation and will cause circulating current in the metal box sheet metal itself. And can cause the sheet metal itself to overheat.

-Bill