You’d be hard-pressed to come up with a trio of operas more diverse in both subject matter and musical character than what feisty West Edge Opera has planned for its upcoming Summer Opera Festival: an ornate Baroque work, replete with vocal and orchestral pyrotechnics, about a triumphant Roman general and his Egyptian queen lover; a singular, sinister and somewhat surreal take on a legendary bigamist’s sixth bride from an early 20th century Impressionist composer; and the American premiere of a 2018 work by a British composer based on a wildly popular, slightly spooky children’s novella by Neil Gaiman.