I know sites where you can connect your shop and then it creates webhooks. (www.myshop.de/admin/2023-04/webhooks.json). So when 100x people connect their shop at the same time at the rate limit are 2 request per second ? how the site owner can create 100x webhooks at the same time ? Or maybe you recieve 75 concurrent webhooks maybe a product was created then you recieve it on your webhook is the rate limit now 2 request per seconds ? So whats the sense of the webhook then ? Thats normal that you recieve more than 10 webhook actions per second if you have 10k users who connected their shop and listen for events maybe product created or sold.
Rate limits are per shop. The rate limit of 2 per second is for API calls to each shop, not webhooks.
Webhooks are just data that hit an endpoint in your app when certain actions happen. If you have code that executes on the reception of a webhook that requires making Shopify API calls, then you may have to throttle them if you're getting a lot of webhooks from the same shop in short periods of time (like more than 1 per second).
API calls follow the leaky bucket method, so for example you could make 10 API calls in a second and they wouldn't fail, because you start out with 40 credits on a normal shop, and the API credits refill at a rate of 2 per second (Shopify Plus gets double the amount of credits and recharge rate).
For details about API call limits see https://shopify.dev/docs/api/usage/rate-limits
For more about webhooks: https://shopify.dev/docs/api/admin-rest/2023-04/resources/webhook