How does this work from a legal and fiscal point of view for the writer?

As a writer, you must ensure that you comply with the laws of your country from both a legal and tax point of view.

To activate my Stripe account, I need to fill in company details, which I don’t have.

The opening of an account on Stripe effectively requires, for its activation, to show that you can receive payments legally. However, it is not necessary to make this activation right now.

You can just start to write roadbooks and then request a transfer to your Stripe account later, once you have reached the minimum amount you have set yourself.

This can happen as soon as you think the amount is large enough, which will then justify the creation of a tax status.