Here are some options depending on the context:
For pace:
* Speed: This is the most general term, but it might not convey the specific feeling of briskness.
* Hustle: This implies a fast and energetic pace, similar to brisk.
* Clip: This is a more informal way to describe a brisk pace.
For manner:
* Liveliness: This captures the feeling of being energetic and animated.
* Vigor: This suggests a strong and energetic approach.
* Promptness: This emphasizes the quickness and efficiency of the action.
Ultimately, the best noun to use will depend on the specific situation and the nuances you want to convey.