Doing portraits in 4x5?
A very interesting question!
Your camera has to be quick, because the person you want to portrait will not hold the position forever.
Your camera has to be simple, because apparative reality is a big obstacle while doing something like social interaction.
You should use a portrait lens, what means 180-300 mm focal length because a huge 4x5 camera will be a huge menace.
You should use a camera on which you can read the bellows extension simply, because doing portraits in 4x5 is macro photography, c.f. the
YAPN macro bellows extension factors chart.
You should use one ore more flashes to get a small aperture like f32, in order to get sufficent depth of field to get the face sharp, not only the nose.
You should use something like a sliding back to change rapidly between ground glass and film holder.
Perhaps you should use a dedicated press camera (Graflex, Busch, Linhof Technika) with a range finder and a flash gun - that's been used for decades to produce good photographs.
Most people used to take a medium format camera like the quicker Mamiya RB67/RZ67. When enlarging your negatives to 8x10 inch, there will be no visible difference between the formats. The bellows factors are indicated on the outside of the camera, You have a reflex viewer and a quick winding lever. You will have a greater range of sharp lenses for this system.
Regards