from your own experience with c2, do you think it's a good practice to use "included" event sheets ?
Others have already given good responses to this, but I'll throw in mine as well:
Yes, I think it's absolutely good practice to use included even sheets. My typical example I usually give is a puzzle game that has elements that are common across the whole game (like a user interface, audio cues and physics behaviours) - these can all be in their own event sheets. Then, each level can have its own event sheet that handles unique properties like background music, level goals, specific challenges, etc. To "activate" your common elements, you simply include them in each level's sheet as needed. You could even take it a step further and chain together includes, so you have one central included event sheet which in turn includes other common event sheets.
There are many ways and reasons to use include, but it usually comes down to re-usability and organisation of code, both of which are massively important for any project of notable size.