Re: "UPS Understanding"
If you have starte lead acid, then its battery designed for C/10 discharge time. In other words, if you want all 200Ah from your battery, fastest time for discharging is 10h with current of 20A. Lowest voltage for your battery (if starter type) is 11,9V (10,5V for deep cycle).
Deep cycle are usually rated C/20 and are not designed for higher currents, specially starting currents, because of that deep cycle batteries are usually linked in big banks of batteries in solar-inverter systems.
Starter type is float battery and are not designed for complete cycle. For longer life discharge up to 30%, and 30% from 200Ah is 60Ah.
Deep cycle type can cycle with complete capacity.
Every inverter have efficiency ratings, this also should be taken in calculations. Just feel that heat which is generated as loss in inverter device.
If you want to get maximum capacity from your battery maximum continuous load is around 200W, if you have stronger loads you cant count on 200Ah.
There is NO 200A for 1h in 200Ah battery!
People usually forget that battery produce power by chemical process which need time and require certain conditions.
Peukert's law
https://en.wikipedia.org/wiki/Peukert's_law