in each you have error amplifier with reference.
in current mode, this then feeds into PWM COmparator with the current sense voltage ramp.
in voltage mode, its exactly the same as that,,,,,BUT................THE error amp output goes into the PWM comparator with a fixed triangle wave into the other input of the pwm comparator
so the only difference is where you get the ramp from.
in current mode, you get it (ramp) from the current sense resistor, in volt mode, you get it from a triangle oscillator.
that is only difference.
nobody tell you this, as it is an industrial secret, and in recession, nobody want you or anyone else to know