Hi Antonio 

Thanks for posting in the community! Lucidchart brace shapes by default have that "Note" text box attached to them. However they can be easily removed by deleting the text. If you will frequently need this brace shape without the text box attached I recommend deleting the text from the brace then saving the brace shape as a custom shape. Then you'll easily be able to drag and drop onto the canvas without having to delete the text box each time. For help with this take a look at our Access Organize and Share Shapes article.

In regard to the custom aspect ratio that is unfortunately currently unsupported in Lucidchart. If that it something you'd like to see in the future please submit this feature request form. Ideas submitted here are shared with the development team for their consideration. Thanks for your help with improving Lucidchart! Please let me know if you have any further questions.