Do I have to bring 1000 euros when traveling with a group in Europe, otherwise I won't be allowed to go through the customs?

This depends on what group you signed up for. If it is all-inclusive, just bring enough cash for your own use (according to your usual consumption habits). Because going to the toilet costs money in Europe, unlike in China, most of them are free. The general charge for going to the toilet is between 0.5 and 1 euro, and some odds and ends of cash are needed to buy some small items, souvenirs and the like. After all, not all shops support credit cards, especially small shops in small towns. If you sign up for a low-cost package tour (there are many self-funded items), then the tour leader (travel agency) requires you to bring 1 1,000 euros in cash, which means that besides your own use, you have to pay for the self-funded items during the trip. Although shopping and participation are not necessary, are there at least so many projects you like? So they all receive cash directly abroad! Then you only need to carry cash with you, and you won't be repatriated because there is too little cash. You will only detain those who have too much to declare!