What's current reliability like? I'm looking to meet a group of friends in July in London, then fly them to Malaga and a few days later onward to Paris.

On the day in question, EasyJet offers multiple LGW-AGP and LTN-AGP. One particular LTN departure (in the middle of the day) is the optimum mix of price and schedule. Is there any significant risk of its being cancelled? The one later LTN flight would present the risk of our car rental or accommodation reception being after hours, and getting to LGW or LHR for another flight on possibly another airline would be a wrinkle.

How about AGP-CDG, afternoon departure? Should that be pretty reliable?

In general, a delay of an hour or two isn't a big concern, but not getting to the destination at all would be.

You really are in crystal ball territory here. Impossible to offer you any meaningful information. EZY are not too bad with punctuality and reliability, I’d be choosing the flights that fit your plans best and hope all goes more or less to the timetable. There are no scheduling guarantees in aviation, too many variables that just might not align on any particular day.

The only guide I apply is that the first flight of the morning is likely to be on stand and depart, all things being equal, reasonably punctually. Any knock on effect from earlier delays always is more likely to impact later departures, however there is padding to the schedules and LCC's are very keen not to be on the ground as much as possible.
Like the stock market the past performance is not necessarily indicative of the future, but U2 are pretty good when dealing with circumstances within their control.

Same as above, I usually try to avoid the last flight of the day if flying LCCs. Knock on wood but I never had cancellation or huge delays with EasyJet....