I personally am a fan of floating alerts such as Toasts. I am thinking of using them for the form validation and feedback.
I find the inline movement of content terrible, though it seems to be the status quo at the moment. What are the pros versus cons of each and which gives a better UX?
Edit: To clarify, I mean the append to body style alerts which cause the content to move.
The question is orientated at validating large forms (20+ fields) rather than a simple sign up form.
I am a fan of keyboard only support so when a field is invalid then I have set up a function to automatically focus on the first invalid input. With the append to body alerts, the alert itself may not be visible, especially on mobile platforms.