> Meanwhile you act as a company with a single B2B client and one invoice a month

There were some changes in this area recently. Paddle is now providing you two reverse invoices each month, one for sales in the USA done by Paddle.com Inc. and one for sales in the rest of the world done by Paddle.com Market Ltd.

For the accounting purposes you have two B2B clients (belonging to the same group). You still receive a single wire transfer though.