Mixed OS networks (95/98, NT, 2000, XP)

Gday all
D4 Pro, Paradox, BDE 5.01

I posted 2 questions following up on my question on mixed OS
networks (95/98, NT, 2000 and XP) but have not had an answer
yet.  The primary answer to my question is that opportunistic
locking should be OFF in NT, 2000 and XP machines when they are
used as a file server.

Here are my next questions again..

Do ALL the XP/2000/NT machines on the network have to have
opportunistic locking turned off, or just the one used as the
file server?

In the network of Win 2000, NT (SP4), XP and the other 95/98
computers, is there a preference as to which OS of the 2000, NT
or XP should be used as the file server?

Thanks all for your comments