[Question:] How to find the OPTIMAL way to know, which updates to integrate....

You can do all this with a sysprep/capture method on a vm.
make a vhd in diskmgmt.msc or diskpart.
detach the vhd and use it as the only hard disk in a vm (I use vmware workstation 10.0.2)

1) Install the desired OS.
2) Do a dism /online feature change of your netfx3 and other features you want to turn on
3) Install the desired language in control panel.
Let it download from the language pack from the WU servers.
4) Run wuapp and download any and all hotfixes and let them install/reboot until you no longer need to install anything.
5) run dism /online /cleanup-image /startcomponentcleanup /resetbase
This will remove any superseded updates.
6) run %windir%\system32\sysprep\sysprep.exe /audit /reboot
7) In audit mode, go into control panel and delete the user account you setup the system with, deleting the user files
8) run the sysprep program (usually present whenever you start audit-mode) with oobe and shutdown options
Whether or not to generalize is up to you. Generalizing removes the Hardware Abstraction Layer configuration info for your specific machine.
I'm sure it probably does other stuff too. It's usually safer to use Generalize option.
9) When machine is shut down, go back into diskmgmt.msc and attach the vhd you used.
10) delete the users\administrator folder from the windows partition of the vhd (usually 2nd drive added since first is the boot drive)
11) capture the vhd using dism

Code:

dism /capture-image /capturedir:H: /imagefile:install.wim /name:"Whatever you want to name it" /description:"The long description that appears at the bottom of the screen during setup"

12) detach the vhd and do whatever you want with the new install.wim

I would recommend staying away from installing any non-ms products in audit mode if you want them to function correctly after setup.
I've found that things that mess with any sort of system settings without installing a proper package such as MS Office, will not work as intended.
Things like winrar file associations or other similar programs that mess with your file associations should be avoided.

 

wimscript.ini is better

Spoiler

Code:

[ExclusionList]
\Users\Administrator
\Windows\Logs\CBS\*
\Windows\Logs\DISM
\Windows\Logs\PBR
\Windows\Panther
\Windows\Prefetch
\Windows\System32\Sysprep\Panther
\Windows\System32\Sysprep\Sysprep_succeeded.tag
\Windows\System32\winevt\Logs\*
\Windows\WinSxS\ManifestCache\*

 

I use a config.ini as well, but I didn't wanna confuse him if he isn't used to capturing any images.