Yeah, both. I don't have it yet, but I was planning to add a way to stop all notes, and possibly individual synthesizers. In terms of pattern, what I've seen is that each pattern has a name, and can be individually stopped/started. I don't show it in the vid, but you can make different named patterns and play different synths at the same time.
In extempore you disable a pattern by using a different operator, I copied that by adding a ! after the pat command.
In the video I stop/start stuff because I haven't yet added the code to have the pattern wait for the next cycle before updating itself. I think I'll need to keep the last pattern around until beat 0 comes around and swap in the updated copy.
I will refresh my memory on Tidal Cycles, and have a look at FoxDot/Ixi lang to see what they do too.