Bavarian Cream is different from superstabilized whipped cream. Bavarian Cream is a combination of creme anglaise, whipped cream and gelatin ( The Vanilla Version ) and superstabilzed whipped cream is whipped cream stabilzed with gelatin. The bavarian cream makes a wonderful filling and you could definitely use the superstabilzed whipped cream for the frosting.
Rose’s deep dark passion chocolate cake is an oil cake, which makes it nice and moist even straight from the fridge. You could also try a sponge/genoise for the cakes.