I think S.Anthonianus has slightly more pointed leaves and yours could be E.Anguliger.
The former has pointed purple and white medium blooms and is notoriously hard to get it to flower, the latter has small fragrant white / yellow blooms and flowers easily. Both bloom in summer.
Re: potting medium. As with all epiphyllums a free draining mix is essential. Cactus/succulent mix would be best.
Good luck.
