Not sure you've solved the complexity when you've just slotted in another front to a general solution that is over-engineered. You could have replaced either scenarios with a single NextJS or SvelteKit solution. Go above and beyond in "complexity", write your Node backend (keeping it one language, JavaScript), and use vanilla HTML and JS to consume that.

To me, htmx isn't as revolutionary as people make it out to be, and possibly that's due to the fact I'm just not burdened by the old days of gigantic Angular apps and massive ASP.Net stacks. My history was mostly JQuery where needed (which was all the time before JS got its act together).