You can find parameters for connection brokers in the DB Admin manual's Reference section under "Database server network parameters".
Some parameters have effect database-wide and are specified on the primary broker, for example -n or -B. Other parameters are specific to connection brokers and are listed in the table linked above, e.g. -Mm or -Mpb. Note that the options available to you are dependent on the OpenEdge release you are using.
For client/server parameters, e.g. -Mm, they apply to the broker for which they are specified. They do not propagate from one to another.
The parameters I know for sure are per broker:
-Mi -Ma -Mpb -N -H -S -Mm
I did a test with a broker started with -Mm 32600 for the primary and -Mm 1400 for the secondary.
Verified message lengths with FOR EACH NO-LOCK and tcpdump.
Additionally I can't think of any other parameters that would make sense on a per secondary broker/manual server setup.
Sr Tech Support Engineer