I didn’t do anything with the USB token, my client used to sign invoices earlier, by downloading it into the local environment.
Then he wanted it to happen automatically, so we went we the vendor.
I don’t remember it correctly now, but It was an HSM box plus some PKC keys(or something like that) needed for that. That too for digital signature.
So, yes you would need to read more, just talk to some vendors who do this, to understand the flow, they will make you understand for free.
I just shared a similar thing that is needed in India, thinking it might help.