Optimal configuration of a research group In most of the European Universities I know, research groups are created from the equivalent of Assistant Professors and the Principal Investigator is voted in some sort of election, where there are elections every 2/4 years. In groups with such profile I have usually seen that scientific output is low and that most of these members are not really motivated to do research and are only affiliated to these groups for CV and promotion purposes. But this is of course my personal experience, I do not state this is always like this. From the other side I know other groups that are created from scratch from somebody with a very good CV, who has a vision and ambition, and who gets all research group members not from Department colleagues but from funding he/she attracts.  All group research lines are derived from her/his experience and CV and scientific output in this case and according to my experience, tends to be high. Based on your personal experience or factual evidences, what is the most optimal configuration for a new research group, the former or the latter or do you think there are other different configurations?
I assume you are basing this on European model, so in my experience the groups based around some common interests are the strongest one because they have a vision that can lead group. Usually these are friends or couples, that succeed to attract funding making multidisciplinary team. In such a team everyone knows each roles and they keep each other back by making sure people are represented in publications in terms of authorship equally. I would suggest you to take a look on Research Gate lab profiles where you can see how members of particular lab are connected and what grants or projects they menage. In my opinion it is the best way to discover dynamic of a group and internal structure. Second things are Center of Excellences, they are now because of HORISONT2020 becoming more popular and are highly hierarchical. However primordial idea for their creation was done trough application of group or consortium of reaserchers and scientist, in there you can observe same things as in your question, however structure is maintained highly hierarchical. In my opinion best way to organise research group is around "friends and family" because you need to trust people in order to follow through with your agenda. I'm not saying that groups that are based around one person are bad, but due to increasing emphasis in academia on teaching, management and bureaucracy, alone PI in current European funding scheme structure can not survive.