The ability of the jet to supply fuel is limited. It is only linear up
to a point. Beyond this, the greater airflow at max rpm would cause a
lean mixture.

No!  Changing the jet size changes the MIXTURE RATIO.  You need to
supply more air and fuel, but in the same proportion, to take full
advantage of the cam.  However, you will recieve some advantage even
with stock carb.

The only reason to change jets is if increased horsepower will cause
overheating. In that case a slight richening of mixture will cool
internal parts.  Generally racing engines are set up pretty rich for
this reason.  If this is for a street machine you probably do not need
to change mixture.

Depending on how much lift and duration the cam has, you may want to
increase carb size.

Rejetting is not necessarily needed.  The usual problem is
getting the vacuum controlled aspects like metering rods and
power valves to open at the correct times to correctly meter
or enrich the mix.

Lugnut

Enlarge which jets? There's often no need to enlarge main jets unless the
choke size has also been increased and no specific reason why the mixture
ratio would change once the engine is at reasonable rpm. However at low rpm
a long duration cam isn't working very efficiently and a bigger idle jet is
often needed to offset the poor "signal" from the venturi. However jetting
is very engine specific and there's never any point guessing. Take the car
to a chassis dyno and have it set up properly.
--
Dave Baker