Yes TGVs are very popular and can sell out days in advance, especially those heading south and to Germany. If you’d like to travel this summer, I wouldn’t wait long before booking. Have a look at this page : https://travel.b-europe.com/Eurail-GE/en/booking-tgv#TravelWish

Seat reservations : there’s a 10€ limited fare and then it costs 20€ until the train is sold out. They reduce flexibility (by a lot) but at least you know that you’ve got a seat.

Most French trains are crowded honestly as they don’t run often…

Thank you for the fast reply! I already got all my seat reservations, but nevertheless am wondering if the trains can get full if everyone needs a seat reservation. don’t want to sit on the floor because i can’t get through to my seat again honestly

Okay then they will most certainly be full but you should be able to get to your seat. Boarding is always a slow process though : people need to go upstairs, etc.

You’ve paid for a seat, you’ll get it, don’t worry :)

As the TGVs have mandatory reservations, there will be no travellers without reservations, unless something extraordinary has happened.