All weather battery max/peak power and usable capacity

I'm trying to decide if one battery will be sufficient for my system or if I need to plan on two right from the start.

What are the maximum and peak POWER specifications for the All weather 280 AH battery?

The spec sheet lists 140 amps continuous but I see 200 amps continuous mentioned in lots of other documentation.

Not knowing the voltage vs current characteristics of the battery, converting amps to watts isn't straight forward!

The spec sheet lists "over current #1 >205 amps for 10 seconds". Seems not much in terms of surge if the battery can provide 200 amps continuous. 205 / 140 is about 145% so if the battery can do 200 amps continuous, I'd expect one battery to provide almost 300 amps for that 10 second surge.

What is the USABLE energy from one battery. Spec sheet lists minimum SOC of 20% which would significantly reduce the usable energy (14.3 down to 11.4 KWH).