Regarding Captcha, this feature is built in to the Wix Studio forms, if a bot is detected captcha is triggered on the live site. No need to add a reCaptcha input field anymore, apparently.
@TobyMcDowell ash4dzyns is correct about the reCaptcha being built in! (stated in the notes here)
You have a lot of great, specific requests, so be sure to submit each as an official feature request through the ‘Request a Feature’ button on the Product Roadmap page!
But like dansuhr mentioned, for the time being you can build the forms separately to get the flexibility you are looking for (which I understand may not be ideal).