Are you Expert?

xHello all,
I have 3 server and soon will have 5.
Server1.acme.loc=root domain
Server2.abc.acme.loc=domain tree
Server3.acme.loc=member server joined to root domain

Is it best to configure the rest of the servers as member
servers to the root domain? Is it better to dcpromo the
servers and have multi tree domains like
acme.loc
abc.acme.loc
def.acme.loc
ghi.acme.loc? and so on.

I also would like to have a central point of
administration especially that each server has a specific
role as an example:
Server1=root domain + exchange server + CA
Server2= application server + share point
Server3=SQL2000 + Oracle 9i

Also I have other geographical sites that include 5
countires. I would like to have a replication process
between these sites for the active directory.