Is there space for a large suitcase if taking a lower berth in the new train 9 and 10?
You put your luggage on the racks at the end of each carriage. If you want to put it on your bed (assume that's what you mean by berth) you can do.
I saw many simply leaving their large suitcases by the side of their berths along the aisles when the seats were turned into beds; and covered them with the "curtains".
If it's not too large the space under the "bed" should also fit the suitcase.