The length of the contents of the tape of any halting TM will be less than or equal to the number of steps it takes to run. Quite trivially: you can’t consume tape without taking a step. For BB(5), 4098 1’s are written to the tape (this is referred to as Σ(5)). As for the length of the contents, I’m not sure, but again you can’t so sume tape without a step, and anecdotally the BBs are generally “back and forth”, at least the Collatz-like ones (which BB(5) is).