There is no recommended maximum number of process control loops (PID) with M340 CPUs, because the loops are executed
only with EFs or EFBs functions.
You should monitor the usable program memory space. After building the application, select PLC tab and Memory Consumption.

Normally with 20 PIDs a BMXP341000 CPU is suitable, but it depends on the rest of the application program.
If you are using many EFBs, EFs or DFBs, the program memory space can be full.

You should also known that performances of the BMXP341000 CPU are lower than the others M340 CPUs (M340 CPUs performances are in the Unity Pro help,
on Modicon M340 Platform\Modicon M340 Hardware\General characteristics of the BMX P34xxxx Processors).