Need expert help on new large battery bank for off grid..

Well, if you must parallel batteries, you are doing it right .    The battery wire from the Charge Controller, keep it short,  but they don't need matched lengths.  And go a size larger if you can, the Classic does not have a voltage sense line, and because of the high charge amps, it's sensed voltage will not be well calibrated,

3,000w inverter @ 46V would be 65 amps.  I'd put 50-70A DC breakers (from Midnight Solar) on each battery string. Mounting breakers might be an issue, because the arc chute wants to be oriented with the breaker upright, as if it were in a panel.  The leads in and out of the breakers count as part of the matched lengths.

Battery cable wires, assume only one string is working , 65A at full load in the inverter would be #4 wire, I'd use #2 - good for 95A, and you need margin so your 70A breaker blows before the wire does.

I'm sure there's some spec that says 60A circuit to be wired with 120% rated wire (72A)

Bus bar to inverter, at least 1/O cable.  There will be starting surges from motors, and you want the inverter to be well fed.

Battery - Battery interconnects, you want something that will flex, and not bend/crack a terminal or case,   Either tinned flat braid, or MT cable.

Reread Mike's post, it's good information. You will not find a better breaker than those made by Midnite Solar.

Two of these enclosures can mount the six breakers, 3 in each.
https://www.solar-electric.com/mnedc-quad.html

This is the breaker used in the enclosure, I believe Mike suggested 70 amp.
https://www.solar-electric.com/pamodccibr.html

Remember, the breakers protect the cable and must be able to carry the full amperage draw of the inverter.

I'm curious about the decision to employ six strings on a part time vacation home. I would have employed more solar and less battery while using 2/0 cables. I'm not an expert of course.

I can't hardly imagine needing more than 12 of those batteries. In fact, I would be inclined to believe that 8 would work fine. FWIW....I have found that good batteries store OK if kept cool and charged over 12.5 volts.

For the simplest, I'd suggest the MRBF fuse blocks and fuses,   A wide selection of fuse ratings.
https://www.bluesea.com/products/2151/Dual_MRBF_Terminal_Fuse_Block_-_30_to_300A
With fuses, you loose an easy way to disconnect one string from the system.

hydraulic is the way to go.   The host site NAWS, has tinned lugs in the store AND the midnight combiner panels
https://www.solar-electric.com/36432.html

please don't use a hammer lug crusher

 > I have it {AC} confined to one small room.

In many cases, I think this is a good way to go.  AC for the entire building might take excessive power - but one very well insulated and air sealed room will be much less while providing a place to escape the heat.  If you want to get fancy, consider adding lots of thermal mass and materials that absorb humidity (sort of a thermal and humidity battery).

If these are indoors in a fairly constant temperature environment, the interconnect cables would be OK.  But if there is a lot of thermal excursions, I'd be concerned that those short interconnects could act like solid rods and stress the battery terminals. Short lengths of heavy wire are pretty stiff, when reinforced with heat shrink

Those are AGM batteries made by Enersys for UPS type duty, rated at 123 ah based at a 20hr rate. They are optimized for high current, short duration output - but they will work fine if you don't deeply cycle them too often.

I could not readily locate DOD/Cycle rating on these, but Enersys batteries of this general type tend to run around 500 cycles at 50% depth of discharge. If you limit it to 25%-30%, you are likely to get closer to 1000 or more charge/discharge cycles from a new set.

In general terms, it is important to provide these batteries an extended float time as often as possible.