Yes, they are. They offer more content in the already rich Watch Dogs 2 world. You get to explore different parts of San Francisco further and engage in new challenges.
There are various side missions. You can find hacking - related side missions where you might need to infiltrate certain facilities to steal data or disrupt operations. Another type could be helping out the citizens of San Francisco with their problems, like rescuing someone from a gang or fixing a corrupted system for a local business.
After the main story in Watch Dogs, there are various side missions. For example, you might have hacking - related side missions where you can infiltrate additional secure systems. There are also missions that involve helping out different characters in the game world, like rescuing someone from a gang or solving a mystery for a local citizen.
It's hard to give an exact figure as it changes with patches and expansions. But typically, there are a substantial number of story missions to keep you engaged for hours.
The exact number of story missions in Watch Dogs 2 is a bit hard to pin down precisely. But roughly, it's somewhere between 35 and 50. This includes the main plot-driven quests and some that have significant impact on the overall story arc.
I think there are quite a few story missions in Watch Dogs 2. But the exact number can vary depending on how you count them and what you consider a main story mission.
It depends on the game. Some games enable you to do side missions post-main story, while others might lock them once the main plot is over. It varies from one game to another.