Hi Alex;
The main thing to remember is that PowerServer's "Connection Pooling" does not work with ODBC connected DBMS. Instead, the Connection Pooling must be done within the ODBC Manager for the related DSN. Otherwise connection pooling could be off for those type of DB connections - even though PS's setting is ON (>0).
The maximum amount of CP'ing will be related to the maximum number of concurrent App threads you anticipate. The minimum should be set for the expected low thread activity that your PS Apps could have. So say for example 5,000 App users where the low end threads are 0 and the high end is 1,000 - I would suggest MIN 5 and MAX 1000.
HTH
Regards ... Chris