Pick Google Forms or Typeform when you describe a form, and the same propose-then-approve flow runs against either one.
One composer, two targets
The provider is a choice you make before you describe the form, not a setting you discover afterwards. Intake proposes the same structure for either, checks it against what that provider can actually express, and shows it to you before anything is created. Typeform supports a different set of question types and a different way of expressing logic, so a proposal that Typeform cannot represent is adjusted before you see it, rather than failing after you have approved it.
Bringing what you already have
A Typeform connection can import the links you have already made, so your library holds forms from both providers instead of only the ones Intake created. Imported forms are marked as imports: Intake can read them and link to them, and it says plainly which ones it did not create.
What is not there yet
Editing a Typeform in place is not implemented. Google Forms can be revised in the account it lives in; a Typeform cannot yet, and the interface says that instead of pretending the two behave the same. Microsoft Forms remains a connection and nothing more. There is no supported API for creating or editing Microsoft Forms, so a Microsoft connection does not imply that form creation works — and it does not.