> The UI I think would require React is a wizard-style form with clientside rendered widgets (eg. tabs).
Can you think of any example sites/web apps which illustrate what you mean? I'm imagining something like VSCode, but AFAIK it's built with a custom JS framework and not React.
Try the EC2 creation page. There are tabs for advanced options, widgets like images selection that you can choose from AWS-managed, Community, your own AMI, etc. And then the next page is confirmation of similar widget which you can go back and edit. I'd imagine that if you render it in backend first and one of the tabs has error your backend form library has to know how to rerender all the widgets that you already implement in JavaScript once. If the page is done in SPA the backend just send the data back and the existing frontend widget just have to rehydrate itself.
Can you think of any example sites/web apps which illustrate what you mean? I'm imagining something like VSCode, but AFAIK it's built with a custom JS framework and not React.