How to get post meta value and post in one query?

When you do a query WordPress already gets the post_meta.

Even though you are calling get_post_meta() It is not performing another query. It is retrieving the value from the post meta cache.

Now if you don’t need the post meta you can set a flag that will eliminate the additional MySql query. To do this you set 'update_post_meta_cache' => false in your args.