Yes to 1st question.... No to 2nd question.... If the air can flow to the FB/CC opening, well above the fire, there is no need to a pipe or deflector.... those additions are for "already made" smokers that needs help....
The upper air vent was "invented" because some folks experienced extreme over temps of the firebox... The design of the smoker choked off the air flow through the cook chamber... too small of an opening below the RF plate and between the firebox and cook chamber... the heat from the fire couldn't get out of the FB and move through the CC.....
To help solve this problem, the first upper air inlet to the FB was installed.... Helped pretty good.... Now the overheated air in the FB could be "pushed" into the CC by outside cold air, as the CC was still warm enough to cause a draft... Then the calculations were investigated and some assumptions were made.... the original design was for a side firebox smoker with tuning plates.... The RF smoker, using the same calculations, was causing increased friction through the smoker... the opening we not big enough..... the calculator was adjusted to allow for good air flow through the RF smoker and everything is good now....