So basically if I don't mind replacing a battery every 2-3 years, I can safely go till 11.4 or 11.6 and not have problems starting the car?
With a good AGM battery, yes, no problem.
With a good long life (calcium) battery, 11.6 should be OK, 1.8 to be safe. You will loose a bit of capacity over time but most car batteries are bigger than needed anyway so loosing 20% capacity over 2 years probably isn't an issue. They also come with a 5 year warranty so if it fails in 2-3 years...
With a traditional cheap maintenance-free lead acid, they sometimes die within 2-3 years anyway due to internal short circuits so it may not be worth worrying about loosing a bit of capacity, but I would stick to 2.0 because they are not designed for significant discharge.
With all these batteries, they should be filled to 100.00% monthly to keep them in good condition, if they never reach 100% then they will loose capacity a lot faster, and 100% means maybe 6 hours charging on the road, or 12 hours on a charger.
Might be worth disconnecting the battery for an hour, measuring the voltage at the battery terminals, re-connecting and seeing how much the voltage drops with the load from your car and cameras and you measuring it at the fusebox. If you see a 0.2 volt drop then you can knock 0.2 volts off the voltage from the discharge graph.
Good car batteries can last 10 years but they often fail before that, replacing the battery every 5 due to heavy use is effectively the extra cost of a battery every 10 years, cheap compared to installing a Cellink Neo. And there is no guarantee the Cellink will last any longer, especially in freezing climates. The
Megtech charging kit with standard USB power banks makes more sense, but is not necessary.