Cosmos Works 6.0 and assemblies with fasteners?

I have got my hands on a Cosmos/works for a short time and I would
like to explore it. I havn't tried looking at the more complex setup
options but so far it has appeared straight forward! Now this is my
first use of this type of software so I have a few basic questions?

When dealing with Assemblies what is the best way to deal with
Fasteners? mainly from the SW Toolbox + a couple of home made
fasteners.

From the toolbax it is possible to get the fastener with threads, but
then how do you define the contact? I am assumeing I should be using
fasteners from the toolbox without threads, ie Simple or cosmetic as
opposed to schematic?

On the other side with hole wizard, how should i be defining the taps?
again there are the options of 'cosmetic threads' and 'call outs' and
these options produce different sized holes for the same tap!

Again if I use a the helicoil insert from hole wizard the resulting
hole is larger than the fastener?

Thanks in advance

Oliver