What tools to bring for road side chain maintenance
Taking a piece of chain can be useful one day, but what is the likelihood? I say take a multitool with a chain-breaking tool, that you verified you are actually strong enough to use (some have very small leverage) and a quicklink. That's good enough for normal rides, unless you are going for a week on your own. Many other people don't take anything. Assess the dangers yourself. On a road bike you are less likely to do more than breaking a single link, on a mountain bike it may be more likely, depending on the kind of your riding.

If you are so worried that you need a full piece of chain you could also nee some spare spokes, tools for removing your cassette (including a wrench with enough leverage) or even a spare rear derailleur (apart from the usual spare hanger). And your torque wrench in case your stem or saddle becomes loose. Ad you will find out it is simply impossible to stuff everything in your saddle bag. Especially if you planned to take two spare tubes as well.