Which subscription should I take at OpenAI?

OpenAI uses two different subscription models. 

1. One for the ChatGPT web-interface (on https://chat.openai.com/); this subscription costs ~$20 USD per month
2. One for the use of their API (on https://platform.openai.com/account/billing/overview); this is a pay-as-you go; prepaid subscription.

To use Fozzels, you would need only number 2.

You can of course provide your credit card to both subscriptions, if you use both. But Fozzels only uses the OpenAI API interface, so only the second subscription is needed to use Fozzels.

To set this up, all you need to do is add your credit card details on the URL provided above.

There is no monthly charge -- only if you use the OpenAI API (through Fozzels) a small amount is charged.

You can find the pricing for OpenAI here: https://openai.com/pricing#language-models

Depending on usage, you can expect an amount of around $0.06 for around every 750 words.

As an indication, this would mean for generating texts for 1000 products, with 200 words each: ~$16 USD. Read more about pricing here.