Can we follow multiple paths, such as Jnana and Hatha, or is it better to focus on one path?

We can follow multiple paths! In chapter 4 of the Gita, Krisna stresses that all paths will lead us to a God Realized existence, but there is a path that is easier than others.

He states that the path of both Karma Yoga and Jnana Yoga are the clearest paths, combined to Enlightenment. But this is for the more informed aspirant, the more devoted.

All paths will lead you to a state of God Realization, but some are easier than others. Kriya is a very difficult path but is known to be the fastest one, many will stumble and fail because of how austere it is. That is why Krisna says that the path of both Karma, action and Jnana, knowledge is the best combination of paths to follow.

They all lead us to the same place but we want to make sure that the path isn't so austere that the students/aspirants lose their way.