The series was pretty okay. This second season is basically what the plot could've been if Jinhyuk, Daeshik and Hyunho had returned/remained on the main team instead of just Eunsoo during the events of Voice 2.

While the overall cases mostly followed the original Voice 2 cases, there were some noticeable changes, like the circumstances of the murder of the new Team Leader were different. The plot involving Kangwoo ends up being split between Higuchi and Ishikawa, with a few adjustments. The plot about Kangwoo being somewhat a loose cannon and as crazy as Jinhyuk was given to Higuchi while Ishikawa getting the PTSD plot that in a way overlaps with Daeshik's similar plot. Eunsoo's plot with her abusive boyfriend was transferred to Komatsu while her role as the secondary leader of the team was transferred to another character. Likewise, the plot involving Seoyul was given to Ogata.

That said, the Doctor Fabre cases were somewhat simplified in this drama and it also had a few changes made. For one, the mastermind's MO and his identifying traits differed. The guy's occupation was also different so it would still get people guessing what the real culprit's identity was. Some of the cases ended up concluding differently than the original series. As much as this second season was based on Voice 2, there are quite a number of twists that should be based on the other Voice seasons. I can't really be sure about that but it does feel like it.

Overall, even if you've seen Voice 2 you should still be able to enjoy this series and be surprised at some of the twists since it wasn't quite an exact adaptation compared to the original Korean series.