It depends I believe.
SSPV broke off the SSPX. SSPX priests are validly but illicitly ordained (SSPX has valid bishops), so if the priest at an SSPV mass is one ordained from SSPX, the Eucharist is valid.
I don’t know if SSPV has been ordaining new priests, but I do not believe any of the SSPX bishops went with them. That being the case, if the SSPV priest saying mass was invalidly ordained then the Eucharist would be invalid.
Regardless of the form of the mass being said or the missal used, I believe all that is required for a valid transubstantiation is the appropriate matter (bread and wine), a validly ordained priest with the correct intention to transubstantiate and the proper words of consecration (this is my body, this is my blood).