How many update (V1 and V2) processes per app. instance should be configured?

Hello colleges,

We have SAP BW system (NW7.3). Hardware platform - AIX. RAM per application instance - 16 GB.

We have some questions related to performance system guidance.

1) How many update (V1 and V2) processes per app. instance should be configured?

2) Can we set up some V1 and V2 processes on different app. instances or on primary app. instance only? Or are there any restrictions?

3) Are there the rules of thumb for BI/BW sizing on that point?

Thank you very much.