1. I like the compressor in the storage area as it is not used otherwise, too hard to access when packed for camping.
Heat has not been an issue and the ob2 has a fan on the head.
2. I pieced my own kit together as the air zenith kit was not available at the time. It is a nice kit though and includes everything needed.
Air tools are possible, any on board air system is capable of running tools if you have a tank, the output of the compressor just refills the tank quicker.
With the 200psi of the ob2, you will need a regulator to reduce the output pressure for air tools as most air tools are designed for 90 psi. I have no issues running air tools, they came in handy while installing Henny's suspension at my house as I do not have an air compressor in my garage.
3. No difference unless you are running air bag suspension on a lowrider.
4. Having a quick disconnect plumbed to the front and back of the truck help make the OBA easier to use. I have a regulator and air dryer/lubricator on quick disconnects so that when using air tools I can regulate the pressure down to 90psi and it removes moisture and adds oil to lubricate my air tools.
Sent from my rooftop tent while stargazing