Another Boltzmann brain can pop up, which contains a short term memory of being previous Boltzmann brain. Sensory inputs aren't constrained though. Most probable sequence of such brains should feel like noise all over your senses, I think.

Another Boltzmann brain can pop up with the result of whatever decision the previous brain could have made, the actual decision it made is irrelevant.

Why? The time passed for the Boltzmann Brain won’t necessarily be tied to its real frame of existence i think, it may simulate any timeframe imaginable, depending on its starting conditions.

In fact the simulation of any timeframe would be constrained by physical laws.

For example for a Boltzmann Brain with a similar chemical composition as ours the speed at which chemical reactions occur would limit the speed of experience.

For a Boltzmann Brain that simulates ours with a very different physical substrate the speed of light would still be a limit.