When running OPS/MVS instances on multiple LPARs inside the same SYSPLEX, is it necessary that each LPAR has a different OPS subsystem like OPSS, OPSA, OPSB, etc?
No, all LPARs can use the same OPS subsystem. The default subsystem id is OPSS.
Different subsystem IDs are only required if multiple OPS instances will run on the same LPAR.
See the reference below for further information: