As MLS awaits potential blockbuster moves for Heung-Min Son and Thomas Müller, clubs like Atlanta and LAFC are already making strategic additions from England’s Championship to boost their rosters.

The summer program—featuring ‘Die Walküre,’ ‘The Marriage of Figaro,’ ‘La Bohème,’ ‘Rigoletto’ and ‘The Turn of the Screw’—offers largely standard repertoire enriched with subtle surprises and ...