Lithium can be economical choice for those with heavy use
Most people I meet boondocking are happy with two Golf Cart (GC) batteries and higher energy consumers will use 4 GC batteries.
Typically a battery is defined as fully charged when the resting voltage is >12.6 volts. Resting voltage is defined as 24hrs with the battery disconnected or with no loads or charge applied.
The battery monitor is critical to make sure you get the most cycles out of your battery.
Most RV converter chargers combine 3 stage battery charging into a dual stage hybrid process. This will lead to shorter life expectancy.
I believe AGM is a great middle ground of battery choice.
Not all Deep Cycle batteries are created equal!