In a Low-JS application of the type supported by Hotwired, Liveview, etc you would only send the HTML elements that are updated not the whole page. That's goin

In a Low-JS application of the type supported by Hotwired, Liveview, etc you would only send the HTML elements that are updated not the whole page. That's going to go over the wire with compression so you're unlikely to loose out much compared to the raw JSON. With an SPA you're going to have to render your data to some form of JSON format e.g. GraphQL and then rerender it again as HTML on the frontend. Without specific examples it's hard to talk meaningfully about performance but conceptually Low-JS is, IMHO, easy to work with and you get the fallback for clients without JavaScript for free. For frontend interactions which don't require new data from the server you can still make use of local JS via something like Stimulus. YMMV.