Correct, Penghus is 100% a must. if it can be taken in the opening few days, it will significantly change the calculation of the defenders as well as the US/Japan/Aus alliance. Rapid loss of critical terrain will either deter the US from intervening, or force them to commit without preparations, either way works to the PLA's advantage.Like others have said, Kinmen or other coastal islands currently under ROC control have close to no military value. All that does would be to spur a more firm western alliance against further military actions.
Pascadores, on the other hand, is probably the most strategic area to take. It would serve as the perfect springboard for many aspects of a full on invasion down the road. Just from a purely military and geopolitical perspecive, taking Kinmen and Matsu would be a liability, where as the Pascadores would be a significant coup, that renders further operations much easier (if enough infrastructures can be built there in the meantime) and more likely to succeed.
militarily, losing Penghu as AD and early warning node will also give the PLA aviation safe airspace in close proximity of Taiwan from which they can conduct surveillance and deliver air-launched ordinance. Moreover, Taiwan will be forced to reorient its defensive posture away from its flanks, allowing PLAN safe passage through the channels into the pacific.