I would for sure get a shelf. It's a cheap easy way to increase floor space in the cage. And personally, i would get a T10 over a T8. I have 3 of both and the little extra for a T10 is so worth it. I also have 3 T25 which imo are awesome
The darker strip under the shelf is a good thing too. It gives the snake a place to curl up and feel secure if it doesnt want to sit in a hide. Mine use the space under the shelves all the time...but then they also use the top of the shelf a lot too lol.