Yes i understand you have some difficulties due to reserved term of wordpress.
As you asked for setting of field sizes, Yes we have better UX for this purpose, If you already have CubeWP Frontend Pro installed then where ever you would like to display custom fields on frontend, There is an option inside our form builder to set field size with “+” and “-” buttons,
But if you are asking about backend as metabox fields, Yes right now we do not have option to set field sizes but the good news is we are working to make our UI and UX better at frontend and backend both, Hopefully you will get particularly this option in future update very soon.
Your 2nd question is about shortcodes for custom field, I just want to tell you every framework or plugin have their own functionality and UX, We have our own UX and we already have given features like form builders to set fields for frontend forms.
If you can ask me your exact requirement like where you want to use custom fields as shortcodes so i can better explain you about that.