Preparing for a baby BRB

[beastul]

I'm hoping to pick up a baby BRB in a couple weeks and I want to have the enclosure all setup and perfect for him.

I've been reading basically all the care sheets I can find and am still torn as far as tub vs tank with plexi top.
I guess I would prefer a tank (currently have a corn and a king in tanks) I like the look of them but I want to do what's best for the snake.

Also I'm having a hard time finding what size tub is best.

As far as tanks, I currently have empty 10, 20, and 30 gallons. To which I'd make a custom plexi top.

I plan on building an custom viv for when he's an adult. But I don't want to stress him with too much room right away.

Thanks for the help!