In a large bowl, using handheld mixer, beat cream, vanilla, and salt on medium-high speed until soft peaks form, about 2 minutes.
In another large bowl, using handheld mixer, beat cream cheese and mascarpone on medium-high speed until smooth, light, and fluffy, about 3 minutes. Scrape down sides of bowl. Add one-third of confectioners' sugar and slowly beat to combine. Continue to add remaining confectioners' sugar in 2 batches, scraping down sides of bowl as needed, until incorporated. Continue to beat on medium-high speed until smooth and creamy, about 2 minutes more.
Using a rubber spatula and working in 2 batches, fold whipped cream into cream cheese mixture.
Using a serrated knife, cut off tops of cakes so surface is flat, if needed. Cut each cake in half horizontally. Place one cake on a platter or cake stand. Using an offset spatula, spread 3 tablespoons jam all the way to the edges. Top with about 1 cup frosting and spread, leaving a 1/2" border. Top with one-quarter of berries, gently pressing into cream. Top with another cake half. Gently press on cake to distribute frosting and help the layers stick together. Repeat process 2 more times.
Using an offset spatula, spread frosting over top and sides of cake. If desired, add a few swooshes. Top with remaining berries.
Refrigerate cake at least 4 hours or up to overnight. Let sit at room temperature 20 minutes before slicing.