[Vuejs]-Is there a way to create a dashboard that only my client interacts with?

You can keep your Nuxt app for the frontend and have a CMS headless for the data, like WordPress (only used to edit/add content via its headless part).

Otherwise, there is also a huge list of tools that could help you in the JAMstack ecosystem: https://jamstack.org/headless-cms/

PS: I recommend discussing about that upfront rather than afterwards.

Yes wordpress will be best because it gives you more control on user roles, you can give them access of content what you want and remove access.

So i think wp is best go for it.