Puerto Rico's ballot structure in essence has a method by which you can look at the votes of those that did not cast Straight ticket, or Party ballots(Votos Integro), (Otherwise known as Votos Mixtos o por candidatura). The gubernatorial results for those that split tickets are shown bellow.
Overall, we can tell that the PIP gubernatorial candidate, Juan Dalmau, relied more on ticket splitters than any other candidate, with the closest being the PPD Candidate Carlos Delgado Altieri.
The Historical tendency of the PPD being dominant ovet the PNP in this election held true, but the PIP overtaking them, and the subsequent down ballot underpereformance by it's candidates presents the case that most of the "PIP" vote was just as a vote in favot of Juan Dalmau, and not vote for the PIP itself.
This is similar for the PPD, as the continuing decrease in vote share for the major parties deliniates that they have more potential losses than the PNP, that was able to better hold on to their base, winning a higher percent of the vote with a significantly lesser share of the Split Ticket vote.
In Summary, the Voto mixto in 2020 presents the case that the PNP, MVC, and PD have stronger bases of support due to their reliance moreso on their Voto integro than the voto mixto, and the reverse for the PIP and PPD, with the latter two holding voters that can more easily switch away from those parties in favor of the first three.