Shiny vs. other server options

I had interesting exchange with Aaron Olsen (are you on here, Aaron?) on Twitter about svgViewR and how it renders in the browser:

My awareness of R servers extends to shiny, plumber and that's about it—it hadn't occurred to me that there were other options for running a web app in R other than Shiny.

Can folks help me understand what the differences are in terms of functionality, performance, etc? My interest in this is more for a package that would serve a web interface locally (as an interactive plot viewer) than as a web app that would be accessed locally. I'm guessing that maybe svgViewR has a focus on performance for complex figures, and that it maybe doesn't need some of the reactivity stuff that shiny includes (or even any kind of server—it looks like maybe it just renders an SVG and open the file in the browser?).