Victron solar set up

Good morning,
I am new to Victron products and I am doing the installation progressively on my own, I own a boat with twin engines so I have two N200 cranking batteries and two N200 deep cycle house batteries plus a cranking battery to start the genset.
So far I have installed 2 only 410 watt solar panels which I have run individual feeds to the engine room, on the engine room rear bulkhead I have installed 2 mppt 30/100 solar controllers that are fused before running to the 2 house batteries so the port and starboard batteries each are charging stand alone.
At the moment there is very little load on any battery while I am absent other than a bilge pump cutting in from time to time so whilst we are only getting winter sunlight the panels have lifted the house batteries up to full. The boat lives on a mooring so before I installed the solar panels it was difficult to get them up to full capacity as they were receiving a charge when the engines or genset was running.
At the moment I have no cross link from the house batteries to the engine cranking batteries nor the genset, however the main cranking batteries are in good condition and crank my Detroit 6v53 over without a problem. I think I may eventually set up a DC to DC charge from the house to the start batteries but for now they are fine so here is my immediate question, I am wanting to install a shunt and some sort of monitoring device that I can see what is happening when I am away from the boat, I am about to install a BUSHMAN 85lt fridge that I want to leave running 24/7 so it will introduce a full time load on the house bank. At the switchboard I have the normal battery switch that can draw from house bank 1, 2 or both. When I leave the boat, this switch is turned off so there is nothing to run the batteries down as the bilge pumps are hot-wired. Should I run a connection direct from 1 battery to run the fridge or should I run a circuit to the main switch and leave the battery switch set the BOTH, so it draws of both banks. I don’t have a problem doing either but I am thinking that if I run from the main switch, it will leave everything live and if I have left something on it could drain the batteries.
I am also moving towards installing an invertor around 3000watt (my whole boat is 12v) after I get the SHUNT sorted, do I need a shunt for each house bank and if so what is the equipment that will give me remote monitoring to both shunts and MPPTs
Finally I should mention that I am about to install a bow and stern thruster, the stern is 12v and will have its own battery and the bow is 24v so it will have 2 12v batteries so although the alternator’s will punch power into them while the engines are running you generally use the thrusters when docking at the end of the trip and the engines are shut down on arrival.
Would I be better to run the thruster batteries charging from the house batteries via a DC-to-DC charger and forget about having the engine cranking batteries connected to the solar system?
If they went flat, I could use jumper leads from the house.
This message has a lot of questions so any help and/or wiring diagrams would help.
I expect further posts won’t be as lengthy as this one I hope to give an overview of the big picture

Welcome to the forum. Per the forum guidelines we do not offer open ended system design support, we will comment on developed designs, but not create them for you. Victron provide a wealth of information with detailed manuals for all products and more general information. You are asking philosophy questions, you need to work out how YOU want your boat systems to work. Some good resources

Victron example schematics

Victron Energy Unlimited book

Victron Wiring Unlimited book

Some comments.

To see all you Victron devices you need a Cerbo GX or an Ekrano GX.

On a Victron system you can only have 1 master house battery, but can monitor many banks in addition. This makes a 1 2 both setup difficult, you may be better wiring them as 1 larger bank.

The above worries me because it highlights a lack of knowledge of fusing. The major source of overcurrent in the MPPT to battery wires is the battery not the MPPT, the fuses MUST be next to the battery not the MPPT. Look at the AYBC or ISO boat wiring standards depending where you are based.

DC to DC chargers can be used for charging bow thruster batteries.

Thank you for your reply
The distance from the mppt solar chargers is about 300mm to each fuse and on the output side of the fuse it is less than one meter to each battery which I thought was within the range required but I would like your opinion as it is very easy to increase the cable length between the mppt and fuse and then decrease the distance from the fuse to the battery
M

The guidance is as short as possible and certainly before any chance of a short to negative wires or ground if cable chafing occurs. Official boat wiring regs is 7" or 200mm unless double insulated inside sleeving or trunking.