welcome aboard.
i have the original with a home made PID with timer, so I say go with the original with PID , The PID id a temperature controller and deepening on model it also controls the smoke generator the Pid generally does not care for how long it is on for and will maintain the set temp, unless you run a ramp soak PId which is good for doing sausages.
as for keeping your eye on a bradley, typically no you dont, it will advance the pucks every 20 mins or so automatically and 1 puck is 20 mins of smoke ... 3 to 4 hours of smoke typically good on most foods,
in a bradley you will see some smokes in the 12 to 18 hour range depending on the meat load.
opening the door will affect the cook time as it has to replace the heat lost first then start cooking again,
there is a v tray and drip pan in the bottom of the smoker that will catch the pucks, extinguish them and catch the drippings .
as for infusing water or any other type of liquid into the meat,,, you can use the water pan after the smoke process is done. in this process you do want to keep the top vent open to aid in air flow and keep moisture from building up in the cabinet and dripping onto the food giving it a bad taste.
the Pid through Auber generally does not have a timer built into it for a cook time duration, there are a few that do and to the best of my knowledge do not need to be used
as for doing any mods .. heater replacements hold off till you use your smoker for a while... then decide on which way you want to go,,, with the exemption getting a pid to use with your smoker
dont worry about the questions that is what were here for