You will definitely need an answer file regardless of which way you want to use, if only for activation purposes.
You can use answer files with any Windows installation media - Windows Setup automatically searches for a file called "autounattend.xml" in either the root folder of the installation media or the root folders of each attached USB media. So you could place it on either a USB installation media or on a separate USB drive.
It can be quite a pain to create your first working answer file - so working with a tutorial and creating the most bare-bone working answer file first and then carefully adding settings to it might be a good idea. Maybe get started with this one: https://www.windowscentral.com/how-create-unattended-media-do-automated-installation-windows-10
Whether you want to install Windows from generic installation media or from your own "golden" image largely depends on what kind of customization you need. You can do a lot of automated configuration to a standard image, but if you need to add or remove drivers, programs etc, you need to create your own image.
You can do this by emoloying these techniques, both of which rely on tools included with Windows:
- Generalizing: You customize a running Windows the way you need it and
then removing machine-specific info like activation and Security
identifiers. It's easy to get started with, but beware: If you plan
to apply Feature Updates with Inplace Upgrade, it won't work Windows
instances based on an image created like this. Here's how it works:
- Offline Servicing involves mounting your the image included in the installation media and making changes to it. This is great for adding drivers, installing Windows updates or removing pre-installed apps. It allows less customization and has a bit more of a learning curve, but Windows installs based on such images can be upgraded via Inplace Upgrade and small incremental changes can be made with a lot less effort. Here's a primer for it: https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/what-is-dism