Here's what I have for both categories. I tried to initially come up with an equal number of both, but I abandoned that, and tried to make a list for each category.
Overrated: Felix, E. Hazard, de Ligt, Werner, L. Hernandez, Donnarumma, Zaniolo, Zaha, A. Traore, Havertz, Ferran Torres, Mount, Rudiger, Fati, Ndidi, Onana, Reus, Olmo, Pavard, Rashica, Kehrer, Guerreiro, J. Gomez, di Maria, Kante, Alisson, D. Costa, Pique
Underrated: Sancho, Kimmich, G. Jesus, de Vrij, Thiago, I. Konate, Abraham, Brandt, Gündogan, Barella, D. Carlos, Jovic, Umtiti, James, Klostermann, B. Mendy, M. Diaby, Demirbay, Tapsoba, Bensabaini, Steffen, Neuhaus, Sommer, Zagadou, G. Martinelli, Greenwood, Handanovic, Busquets, Marcelo, Caravajal, Aubameyang, Payet, Bale, Mascarell, Kutucu