You need to do it by trial and error.
Everyones requirements are different depending on the components in the PC, whether they have a printer or not, what programs they use, etc...
- The safest options to remove are languages/keyboards/fonts.
- Drivers => make sure to NOT remove the drivers for the components in your PC
- If you have a printer, read this [You must be registered and logged in to see this link.].
- If you do not have/want Windows touch apps, then you can remove all the Modern UI components.
- Services => If you want to tweak, use the BlackViper option, otherwise do not touch unless you know for certain it is safe to remove a service..
Then proceed from there, iteratively.